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1.  Do incentives, reminders or reduced burden improve healthcare professional response rates in postal questionnaires? two randomised controlled trials 
Healthcare professional response rates to postal questionnaires are declining and this may threaten the validity and generalisability of their findings. Methods to improve response rates do incur costs (resources) and increase the cost of research projects. The aim of these randomised controlled trials (RCTs) was to assess whether 1) incentives, 2) type of reminder and/or 3) reduced response burden improve response rates; and to assess the cost implications of such additional effective interventions.
Two RCTs were conducted. In RCT A general dental practitioners (dentists) in Scotland were randomised to receive either an incentive; an abridged questionnaire or a full length questionnaire. In RCT B non-responders to a postal questionnaire sent to general medical practitioners (GPs) in the UK were firstly randomised to receive a second full length questionnaire as a reminder or a postcard reminder. Continued non-responders from RCT B were then randomised within their first randomisation to receive a third full length or an abridged questionnaire reminder. The cost-effectiveness of interventions that effectively increased response rates was assessed as a secondary outcome.
There was no evidence that an incentive (52% versus 43%, Risk Difference (RD) -8.8 (95%CI −22.5, 4.8); or abridged questionnaire (46% versus 43%, RD −2.9 (95%CI −16.5, 10.7); statistically significantly improved dentist response rates compared to a full length questionnaire in RCT A. In RCT B there was no evidence that a full questionnaire reminder statistically significantly improved response rates compared to a postcard reminder (10.4% versus 7.3%, RD 3 (95%CI −0.1, 6.8). At a second reminder stage, GPs sent the abridged questionnaire responded more often (14.8% versus 7.2%, RD −7.7 (95%CI −12.8, -2.6). GPs who received a postcard reminder followed by an abridged questionnaire were most likely to respond (19.8% versus 6.3%, RD 8.1%, and 9.1% for full/postcard/full, three full or full/full/abridged questionnaire respectively). An abridged questionnaire containing fewer questions following a postcard reminder was the only cost-effective strategy for increasing the response rate (£15.99 per response).
When expecting or facing a low response rate to postal questionnaires, researchers should carefully identify the most efficient way to boost their response rate. In these studies, an abridged questionnaire containing fewer questions following a postcard reminder was the only cost-effective strategy. An increase in response rates may be explained by a combination of the number and type of contacts. Increasing the sampling frame may be more cost-effective than interventions to prompt non-responders. However, this may not strengthen the validity and generalisability of the survey findings and affect the representativeness of the sample.
PMCID: PMC3508866  PMID: 22891875
2.  Increasing response to a postal survey of sedentary patients – a randomised controlled trial [ISRCTN45665423] 
A systematic review identified a range of methods, which can influence response rates. However, analysis specific to a healthcare setting, and in particular, involving people expected to be poor responders, was missing, We examined the effect of pre-warning letters on response rates to a postal survey of sedentary patients whom we expected a low rate of response.
Participants were randomised to receive a pre-warning letter or no pre-warning letter, seven days before sending the main questionnaire. The main questionnaire included a covering letter and pre-paid return envelope. After seven days, non-responders were sent a reminder letter and seven days later, another reminder letter with a further copy of the questionnaire and return envelope.
627 adults, with a mean age of 48 years (SD 13, range 18 to 78) of whom 69.2% (434/627) were women, were randomised. 49.0% (307/627) of patients were allocated to receive a pre-warning letter and 51.0% (320/627) no pre-warning letter, seven days in advance of posting the main questionnaire. The final response rate to the main questionnaire was 30.0% (92/307) amongst those sent a pre-warning letter and 20.9% (67/320) not sent a pre-warning letter, with an adjusted odds ratio of 1.60 (95% CI 1.1, 2.30).
The relatively low cost method of sending a pre-warning letter had a modest impact on increasing response rates to a postal questionnaire sent to a group of patients for whom a low response rate was anticipated. Investigators should consider incorporating this simple intervention when conducting postal surveys, to reduce the potential for nonresponse bias and to increase the study power. Methods other than postal surveys may be needed however when a low response rate to postal surveys is likely.
PMCID: PMC534787  PMID: 15537429
3.  International health policy survey in 11 countries: assessment of non-response bias in the Norwegian sample 
International health policy surveys are used to compare and evaluate health system performance, but little is known about the effects of non-response. The objective of this study was to assess the effects of non-response in the Norwegian part of the Commonwealth Fund international health policy survey in 2009.
As part of an international health policy survey in 2009 a cross-sectional survey was conducted in Norway among a representative sample of Norwegian general practitioners. 1 400 randomly selected GPs were sent a postal questionnaire including questions about the Norwegian health care system, the quality of the GPs' own practice and the cooperation with specialist health care. The survey included three postal reminders and a telephone follow-up of postal non-respondents. The main outcome measures were increase in response rate for each reminder, the effects of demographic and practice variables on response, the effects of non-response on survey estimates, and the cost-effectiveness of each reminder.
After three postal reminders and one telephone follow-up, the response rate was 59.1%. Statistically significant differences between respondents and non-respondents were found for three variables; group vs. solo practice (p = 0.01), being a specialist or not (p < 0.001) and municipality centrality (least central vs. most central, p = 0.03). However, demographic and practice variables had little association with five outcome variables and the overall survey estimates changed little with additional reminders. In addition, the cost-effectiveness of the final reminders was poor.
The response rate in the Norwegian survey was satisfactory, and the effect of non-response was small indicating adequate representativeness. The cost-effectiveness of the final reminders was poor. The Norwegian findings strengthen the international project, but restrictions in generalizability warrant further study in other countries.
PMCID: PMC2833149  PMID: 20146819
4.  The Effectiveness of Mobile-Health Technologies to Improve Health Care Service Delivery Processes: A Systematic Review and Meta-Analysis 
PLoS Medicine  2013;10(1):e1001363.
Caroline Free and colleagues systematically review controlled trials of mobile technology interventions to improve health care delivery processes and show that current interventions give only modest benefits and that high-quality trials measuring clinical outcomes are needed.
Mobile health interventions could have beneficial effects on health care delivery processes. We aimed to conduct a systematic review of controlled trials of mobile technology interventions to improve health care delivery processes.
Methods and Findings
We searched for all controlled trials of mobile technology based health interventions using MEDLINE, EMBASE, PsycINFO, Global Health, Web of Science, Cochrane Library, UK NHS HTA (Jan 1990–Sept 2010). Two authors independently extracted data on allocation concealment, allocation sequence, blinding, completeness of follow-up, and measures of effect. We calculated effect estimates and we used random effects meta-analysis to give pooled estimates.
We identified 42 trials. None of the trials had low risk of bias. Seven trials of health care provider support reported 25 outcomes regarding appropriate disease management, of which 11 showed statistically significant benefits. One trial reported a statistically significant improvement in nurse/surgeon communication using mobile phones. Two trials reported statistically significant reductions in correct diagnoses using mobile technology photos compared to gold standard. The pooled effect on appointment attendance using text message (short message service or SMS) reminders versus no reminder was increased, with a relative risk (RR) of 1.06 (95% CI 1.05–1.07, I2 = 6%). The pooled effects on the number of cancelled appointments was not significantly increased RR 1.08 (95% CI 0.89–1.30). There was no difference in attendance using SMS reminders versus other reminders (RR 0.98, 95% CI 0.94–1.02, respectively). To address the limitation of the older search, we also reviewed more recent literature.
The results for health care provider support interventions on diagnosis and management outcomes are generally consistent with modest benefits. Trials using mobile technology-based photos reported reductions in correct diagnoses when compared to the gold standard. SMS appointment reminders have modest benefits and may be appropriate for implementation. High quality trials measuring clinical outcomes are needed.
Please see later in the article for the Editors' Summary
Editors’ Summary
Over the past few decades, computing and communication technologies have changed dramatically. Bulky, slow computers have been replaced by portable devices that can complete increasingly complex tasks in less and less time. Similarly, landlines have been replaced by mobile phones and other mobile communication technologies that can connect people anytime and anywhere, and that can transmit text messages (short message service; SMS), photographs, and data at the touch of a button. These advances have led to the development of mobile-health (mHealth)—the use of mobile computing and communication technologies in health care and public health. mHealth has many applications. It can be used to facilitate data collection and to encourage health-care consumers to adopt healthy lifestyles or to self-manage chronic conditions. It can also be used to improve health-care service delivery processes by targeting health-care providers or communication between these providers and their patients. So, for example, mobile technologies can be used to provide clinical management support in settings where there are no specialist clinicians, and they can be used to send patients test results and timely reminders of appointments.
Why Was This Study Done?
Many experts believe that mHealth interventions could greatly improve health-care delivery processes, particularly in resource-poor settings. The results of several controlled trials (studies that compare the outcomes of people who do or do not receive an intervention) of mHealth interventions designed to improve health-care delivery processes have been published. However, these data have not been comprehensively reviewed, and the effectiveness of this type of mHealth intervention has not been quantified. Here, the researchers rectify this situation by undertaking a systematic review and meta-analysis of controlled trials of mobile technology-based interventions designed to improve health-care service delivery processes. A systematic review is a study that uses predefined criteria to identify all the research on a given topic; a meta-analysis is a statistical approach that is used to pool the results of several independent studies.
What Did the Researchers Do and Find?
The researchers identified 42 controlled trials that investigated mobile technology-based interventions designed to improve health-care service delivery processes. None of the trials were of high quality—many had methodological problems likely to affect the accuracy of their findings—and nearly all were undertaken in high-income countries. Thirty-two of the trials tested interventions directed at health-care providers. Of these trials, seven investigated interventions providing health-care provider education, 18 investigated interventions supporting clinical diagnosis and treatment, and seven investigated interventions to facilitate communication between health-care providers. Several of the trials reported that the tested intervention led to statistically significant improvements (improvements unlikely to have happened by chance) in outcomes related to disease management. However, two trials that used mobile phones to transmit photos to off-site clinicians for diagnosis reported significant reductions in correct diagnoses compared to diagnosis by an on-site specialist. Ten of the 42 trials investigated interventions targeting communication between health-care providers and patients. Eight of these trials investigated SMS-based appointment reminders. Meta-analyses of the results of these trials indicated that using SMS appointment reminders significantly but modestly increased patient attendance compared to no reminders. However, SMS reminders were no more effective than postal or phone call reminders, and texting reminders to patients who persistently missed appointments did not significantly change the number of cancelled appointments.
What Do These Findings Mean?
These findings indicate that some mHealth interventions designed to improve health-care service delivery processes are modestly effective, but they also highlight the need for more trials of these interventions. Specifically, these findings show that although some interventions designed to provide support for health-care providers modestly improved some aspects of clinical diagnosis and management, other interventions had deleterious effects—most notably, the use of mobile technology–based photos for diagnosis. In terms of mHealth interventions targeting communication between health-care providers and patients, the finding that SMS appointment reminders have modest benefits suggests that implementation of this intervention should be considered, at least in high-income settings. However, the researchers stress that more trials are needed to robustly establish the ability of mobile technology-based interventions to improve health-care delivery processes. These trials need to be of high quality, they should be undertaken in resource-limited settings as well as in high-income countries, and, ideally, they should consider interventions that combine mHealth and conventional approaches.
Additional Information
Please access these Web sites via the online version of this summary at
A related PLOS Medicine Research Article by Free et al. investigates the effectiveness of mHealth technology-based health behavior change and disease management interventions for health-care consumers
Wikipedia has a page on mHealth (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
mHealth: New horizons for health through mobile technologies is a global survey of mHealth prepared by the World Health Organization’s Global Observatory for eHealth (eHealth is health-care practice supported by electronic processes and communication)
The mHealth in Low-Resource Settings website, which is maintained by the Netherlands Royal Tropical Institute, provides information on the current use, potential, and limitations of mHealth in low-resource settings
The US National Institutes of Health Fogarty International Center provides links to resources and information about mHealth
PMCID: PMC3566926  PMID: 23458994
5.  A Comparison of a Postal Survey and Mixed-Mode Survey Using a Questionnaire on Patients’ Experiences With Breast Care 
The Internet is increasingly considered to be an efficient medium for assessing the quality of health care seen from the patients’ perspective. Potential benefits of Internet surveys such as time efficiency, reduced effort, and lower costs should be balanced against potential weaknesses such as low response rates and accessibility for only a subset of potential participants. Combining an Internet questionnaire with a traditional paper follow-up questionnaire (mixed-mode survey) can possibly compensate for these weaknesses and provide an alternative to a postal survey.
To examine whether there are differences between a mixed-mode survey and a postal survey in terms of respondent characteristics, response rate and time, quality of data, costs, and global ratings of health care or health care providers (general practitioner, hospital care in the diagnostic phase, surgeon, nurses, radiotherapy, chemotherapy, and hospital care in general).
Differences between the two surveys were examined in a sample of breast care patients using the Consumer Quality Index Breast Care questionnaire. We selected 800 breast care patients from the reimbursement files of Dutch health insurance companies. We asked 400 patients to fill out the questionnaire online followed by a paper reminder (mixed-mode survey) and 400 patients, matched by age and gender, received the questionnaire by mail only (postal survey). Both groups received three reminders.
The respondents to the two surveys did not differ in age, gender, level of education, or self-reported physical and psychological health (all Ps > .05). In the postal survey, the questionnaires were returned 20 days earlier than in the mixed-mode survey (median 12 and 32 days, respectively; P < .001), whereas the response rate did not differ significantly (256/400, 64.0% versus 242/400, 60.5%, respectively; P = .30). The costs were lower for the mixed-mode survey (€2 per questionnaire). Moreover, there were fewer missing items (3.4% versus 4.4%, P = .002) and fewer invalid answers (3.2% versus 6.2%, P < .001) in the mixed-mode survey than in the postal survey. The answers of the two respondent groups on the global ratings did not differ. Within the mixed-mode survey, 52.9% (128/242) of the respondents filled out the questionnaire online. Respondents who filled out the questionnaire online were significantly younger (P < .001), were more often highly educated (P = .002), and reported better psychological health (P = .02) than respondents who filled out the paper questionnaire. Respondents to the paper questionnaire rated the nurses significantly more positively than respondents to the online questionnaire (score 9.2 versus 8.4, respectively; χ2 1 = 5.6).
Mixed-mode surveys are an alternative method to postal surveys that yield comparable response rates and groups of respondents, at lower costs. Moreover, quality of health care was not rated differently by respondents to the mixed-mode or postal survey. Researchers should consider using mixed-mode surveys instead of postal surveys, especially when investigating younger or more highly educated populations.
PMCID: PMC3222165  PMID: 21946048
Data collection; health care quality; consumer satisfaction; breast cancer; patient preferences; health care quality indicator
6.  Comparison of response rates and cost-effectiveness for a community-based survey: postal, internet and telephone modes with generic or personalised recruitment approaches 
Epidemiological research often requires collection of data from a representative sample of the community or recruitment of specific groups through broad community approaches. The population coverage of traditional survey methods such as mail-outs to residential addresses, and telephone contact via public directories or random-digit-dialing is declining and survey response rates are falling. There is a need to explore new sampling frames and consider multiple response modes including those offered by changes in telecommunications and internet technology.
We evaluated response rates and cost-effectiveness for three modes of survey administration (postal invitation/postal survey, postal invitation/internet survey and postal invitation/telephone survey) and two styles of contact approach (personalised and generic) in a community survey of greywater use. Potential respondents were contacted only once, with no follow up of non-responders.
The telephone survey produced the highest adjusted response rate (30.2%), followed by the personalised postal survey (10.5%), generic postal survey (7.5%) and then the internet survey (4.7% for the personalised approach and 2.2% for the generic approach). There were some differences in household characteristics and greywater use rates between respondents to different survey modes, and between respondents to personalised and generic approaches. These may be attributable to the differing levels of motivations needed for a response, and varying levels of interest in the survey topic among greywater users and non-users. The generic postal survey had the lowest costs per valid survey received (Australian $22.93), followed by the personalised postal survey ($24.75).
Our findings suggest that postal surveys currently remain the most economic option for population-based studies, with similar costs for personalised and generic approaches. Internet surveys may be effective for specialised groups where email lists are available for initial contact, but barriers other than household internet access still exist for community-based surveys. Given the increasing recruitment challenges facing community-based studies, there is an imperative to gather contemporary comparative data on different survey modes and recruitment approaches in order to determine their strengths, limitations and costs. Researchers also need to document and report on the potential biases in the target and respondent populations and how this may affect the data collected.
PMCID: PMC3502082  PMID: 22938205
Survey methods; Postal survey; Telephone survey; Internet survey; Cost-effectiveness
7.  The effectiveness of recruitment strategies on general practitioner’s survey response rates – a systematic review 
Low survey response rates in general practice are common and lead to loss of power, selection bias, unexpected budgetary constraints and time delays in research projects.
Objective: To assess the effectiveness of recruitment strategies aimed at increasing survey response rates among GPs.
Design: Systematic review.
Search methods: MEDLINE (OVIDSP, 1948-2012), EMBASE (OVIDSP, 1980-2012), Evidence Based Medicine Reviews (OVIDSP, 2012) and references of included papers were searched. Major search terms included GPs, recruitment strategies, response rates, and randomised controlled trials (RCT).
Selection criteria: Cluster RCTs, RCTs and factorial trial designs that evaluate recruitment strategies aimed at increasing GP survey response rates.
Data collection and analysis: Abstracts identified by the search strategy were reviewed and relevant articles were retrieved. Each full-text publication was examined to determine whether it met the predetermined inclusion criteria. Data extraction and study quality was assessed by using predetermined checklists.
Monetary and nonmonetary incentives were more effective than no incentive with monetary incentives having a slightly bigger effect than nonmonetary incentives. Large incentives were more effective than small incentives, as were upfront monetary incentives compared to promised monetary incentives. Postal surveys were more effective than telephone or email surveys. One study demonstrated that sequentially mixed mode (online survey followed by a paper survey with a reminder) was more effective than an online survey or the combination of an online and paper survey sent similtaneously in the first mail out. Pre-contact with a phonecall from a peer, personalised packages, sending mail on Friday, and using registered mail also increased response rates in single studies. Pre-contact by letter or postcard almost reached statistical signficance.
GP survey response rates may improve by using the following strategies: monetary and nonmonetary incentives, larger incentives, upfront monetary incentives, postal surveys, pre-contact with a phonecall from a peer, personalised packages, sending mail on Friday, and using registered mail. Mail pre-contact may also improve response rates and have low costs. Improved reporting and further trials, including sequential mixed mode trials and social media, are required to determine the effectiveness of recruitment strategies on GPs' response rates to surveys.
PMCID: PMC4059731  PMID: 24906492
8.  Reliability of patient-reported functional outcome in a joint replacement registry 
Acta Orthopaedica  2013;84(1):12-17.
Background and purpose
Patient-reported outcome measures (PROMs) are used by some arthroplasty registries to evaluate results after surgery, but non-response may bias the results. The aim was to identify a potential bias in the outcome scores of subgroups in a cohort of patients from the Danish Shoulder Arthroplasty Registry (DSR) and to characterize non-responders.
Patient-reported outcome of 787 patients operated in 2008 was assessed 12 months postoperatively using the Western Ontario Osteoarthritis of the Shoulder (WOOS) index. In January 2012, non-responders and incomplete responders were sent a postal reminder. Non-responders to the postal reminder were contacted by telephone. Total WOOS score and WOOS subscales were compared for initial responders (n = 509), responders to the postal reminder (n = 156), and responders after telephone contact (n = 27). The predefined variables age, sex, diagnosis, geographical region, and reoperation rate were compared for responding and non-responding cohorts.
A postal reminder increased the response rate from 65% (6% incomplete) to 80% (3% incomplete) and telephone contact resulted in a further increase to 82% (2% incomplete). We did not find any statistically significant differences in total WOOS score or in any of the WOOS subscales between responders to the original questionnaire, responders to the postal reminder, and responders after telephone contact. However, a trend of worse outcome for non-responders was found. The response rate was lower in younger patients.
Non-responders did not appear to bias the overall results after shoulder replacement despite a trend of worse outcome for a subgroup of non-responders. As response rates rose markedly by the use of postal reminders, we recommend the use of reminders in arthroplasty registries using PROMs.
PMCID: PMC3584596  PMID: 23343374
9.  The Effect of Low Survey Response Rates on Estimates of Alcohol Consumption in a General Population Survey 
PLoS ONE  2012;7(4):e35527.
Response rates for surveys of alcohol use are declining for all modes of administration (postal, telephone, face-to-face). Low response rates may result in estimates that are biased by selective non-response. We examined non-response bias in the NZ GENACIS survey, a postal survey of a random electoral roll sample, with a response rate of 49.5% (n = 1924). Our aim was to estimate the magnitude of non-response bias in estimating the prevalence of current drinking and heavy episodic (binge) drinking.
We used the “continuum of resistance” model to guide the investigation. In this model the likelihood of response by sample members is related to the amount of effort required from the researchers to elicit a response. First, the demographic characteristics of respondents and non-respondents were compared. Second, respondents who returned their questionnaire before the first reminder (early), before the second reminder (intermediate) or after the second reminder (late) were compared by demographic characteristics, 12-month prevalence of drinking and prevalence of binge drinking.
Demographic characteristics and prevalence of binge drinking were significantly different between late respondents and early/intermediate respondents, with the demographics of early and intermediate respondents being similar to people who refused to participate while late respondents were similar to all other non-respondents. Assuming non-respondents who did not actively refuse to participate had the same drinking patterns as late respondents, the prevalence of binge drinking amongst current drinkers was underestimated. Adjusting the prevalence of binge drinkers amongst current drinkers using population weights showed that this method of adjustment still resulted in an underestimate of the prevalence.
The findings suggest non-respondents who did not actively refuse to participate are likely to have similar or more extreme drinking behaviours than late respondents, and that surveys of health compromising behaviours such as alcohol use are likely to underestimate the prevalence of these behaviours.
PMCID: PMC3332039  PMID: 22532858
10.  Surveying general practitioners: does a low response rate matter? 
BACKGROUND: Primary care has long been of interest to policy research. Recently, there is evidence to suggest that it is becoming more difficult to encourage GPs (general practitioners) to participate in surveys. As low response rates can introduce bias into survey results, it is important to study the effects of non-response. AIM: To assess the validity of a response rate of 44% obtained in a national postal study of GPs surveyed about their work with alcohol-misusing patients by assessing the extent of any non-response bias. METHOD: A telephone survey of 148 GPs who had not responded to repeated mailings of a postal questionnaire was undertaken. In addition to personal and practice structure characteristics, the GPs were asked three questions taken from the original questionnaire about their work with alcohol-misusing patients. RESULTS: Of the 148 GPs telephoned, 64 responded to the telephone questionnaire in full; all had previously failed to respond to the postal questionnaire. Younger GPs were more likely to respond to both the national postal and telephone surveys, but more so to the latter. Telephone responders were more likely to be GPs in a single-handed practice. The work of GPs with alcohol-misusing patients highlighted differences between the two response groups. Male telephone responders were found to be identifying a significantly higher average of alcohol misusers than male postal responders. Telephone responders were more likely to feel trained in treating alcohol misuse and to feel better supported to deal with this patient group. CONCLUSION: Some significant differences were identified, indicating the presence of non-response bias. A low response rate need not affect the validity of the data collected, but it is still necessary to test for non-response effects and make corrections to the original data in order to maximize validity.
PMCID: PMC1312913  PMID: 9101692
11.  A confidence interval approach to investigating non-response bias and monitoring response to postal questionnaires. 
STUDY OBJECTIVE--The aim was to develop an alternative method of investigating non-response bias in postal surveys, including a method of calculating a final full (100%) coverage confidence interval which avoids the wide intervals of existing approaches. DESIGN AND SETTING--As part of a two stage survey of disablement in the community, a first phase postal questionnaire was sent to 25,168 households in Calderdale, West Yorkshire, England. Confidence intervals were calculated to investigate the precision of estimates using a "no bias" model, where the prevalence in non-responders is assumed to be the same as in responders. RESPONDENTS--A total of 21,889 postal questionnaires were returned (87%), representing households containing 42,826 people aged 16 years and over. This was achieved by the original post (1st wave, 57% response); two further postal follow ups (2nd and 3rd waves, taking the response to 73% and 81% respectively), the latter including a small personal call back; and a final postal follow up (the 4th wave). RESULTS--The cumulative estimated prevalence of those with dependence was plotted as the survey progressed. The final wave full coverage estimated prevalence for those aged 16-64 years was 12.8 per 1000 with 95% confidence intervals of 11.3-14.4 per 1000. The integrity of this estimate holds as long as the true prevalence in non-responders is within the calculated non-response confidence interval under the no bias assumption, 9.7-16.0 per 1000 people. This latter interval represents the tolerance of prevalence in non-responders implied by the no bias assumption. CONCLUSIONS--The findings have general implications for monitoring non-response bias in postal screening questionnaires. The confidence interval approach developed in this paper offers an alternative to existing regression based estimates, giving an indication of the range of prevalence amongst non-responders that could be tolerated before the no bias assumption used by the model is breached. It is suggested that this approach can be used to determine both the extent of bias, and to aid decision making about the appropriate juncture to terminate follow up. It highlights the potential, particularly in the context of a computerised survey operation, of methodological investigation occurring simultaneously with survey operation.
PMCID: PMC1060708  PMID: 1828494
12.  Effect of questionnaire length, personalisation and reminder type on response rate to a complex postal survey: randomised controlled trial 
Minimising participant non-response in postal surveys helps to maximise the generalisability of the inferences made from the data collected. The aim of this study was to examine the effect of questionnaire length, personalisation and reminder type on postal survey response rate and quality and to compare the cost-effectiveness of the alternative survey strategies.
In a pilot study for a population study of travel behaviour, physical activity and the environment, 1000 participants sampled from the UK edited electoral register were randomly allocated using a 2 × 2 factorial design to receive one of four survey packs: a personally addressed long (24 page) questionnaire pack, a personally addressed short (15 page) questionnaire pack, a non-personally addressed long questionnaire pack or a non-personally addressed short questionnaire pack. Those who did not return a questionnaire were stratified by initial randomisation group and further randomised to receive either a full reminder pack or a reminder postcard. The effects of the survey design factors on response were examined using multivariate logistic regression.
An overall response rate of 17% was achieved. Participants who received the short version of the questionnaire were more likely to respond (OR = 1.48, 95% CI 1.06 to 2.07). In those participants who received a reminder, personalisation of the survey pack and reminder also increased the odds of response (OR = 1.44, 95% CI 1.01 to 1.95). Item non-response was relatively low, but was significantly higher in the long questionnaire than the short (9.8% vs 5.8%; p = .04). The cost per additional usable questionnaire returned of issuing the reminder packs was £23.1 compared with £11.3 for the reminder postcards.
In contrast to some previous studies of shorter questionnaires, this trial found that shortening a relatively lengthy questionnaire significantly increased the response. Researchers should consider the trade off between the value of additional questions and a larger sample. If low response rates are expected, personalisation may be an important strategy to apply. Sending a full reminder pack to non-respondents appears a worthwhile, albeit more costly, strategy.
PMCID: PMC3110121  PMID: 21548947
13.  Effects of a Financial Incentive on Health Researchers’ Response to an Online Survey: a Randomized Controlled Trial 
Nonresponse to questionnaires can affect the validity of surveys and introduce bias. Offering financial incentives can increase response rates to postal questionnaires, but the effect of financial incentives on response rates to online surveys is less clear.
As part of a survey, we aimed to test whether knowledge of a financial incentive would increase the response rate to an online questionnaire.
A randomized controlled trial of 485 UK-based principal investigators of publicly funded health services and population health research. Participants were contacted by email and invited to complete an online questionnaire via an embedded URL. Participants were randomly allocated to groups with either “knowledge of” or “no knowledge of” a financial incentive (£10 Amazon gift voucher) to be provided on completion of the survey. At the end of the study, gift vouchers were given to all participants who completed the questionnaire regardless of initial randomization status. Four reminder emails (sent from the same email address as the initial invitation) were sent out to nonrespondents at one, two, three, and four weeks; a fifth postal reminder was also undertaken. The primary outcome measure for the trial was the response rate one week after the second reminder. Response rate was also measured at the end of weeks one, two, three, four, and five, and after a postal reminder was sent.
In total, 243 (50%) questionnaires were returned (232 completed, 11 in which participation was declined). One week after the second reminder, the response rate in the “knowledge” group was 27% (66/244) versus 20% (49/241) in the “no knowledge” group (χ21 = 3.0, P = .08). The odds ratio for responding among those with knowledge of an incentive was 1.45 (95% confidence interval [CI] 0.95 - 2.21). At the third reminder, participants in the “no knowledge” group were informed about the incentive, ending the randomized element of the study. However we continued to follow up all participants, and from reminder three onwards, no significant differences were observed in the response rates of the two groups.
Knowledge of a financial incentive did not significantly increase the response rate to an online questionnaire. Future surveys should consider including a randomized element to further test the utility of offering incentives of other types and amounts to participate in online questionnaires.
Trial Registration
ISRCTN59912797; (Archived by WebCite at
PMCID: PMC2885780  PMID: 20457556
Questionnaires; Electronic Mail; Randomized Controlled Trial; Reminder Systems; reward
14.  Who does not participate in a follow-up postal study? a survey of infertile couples treated by in vitro fertilization 
A good response rate has been considered as a proof of a study’s quality. Decreasing participation and its potential impact on the internal validity of the study are of growing interest. Our objective was to assess factors associated with contact and response to a postal survey in a epidemiological study of the long-term outcome of IVF couples.
The DAIFI study is a retrospective cohort including 6,507 couples who began an IVF program in 2000-2002 in one of the eight participating French IVF centers. Medical data on all 6,507 couples were obtained from IVF center databases, and information on long-term outcome was available only for participants in the postal survey (n = 2,321). Logistic regressions were used to assess firstly factors associated with contact and secondly factors associated with response to the postal questionnaire among contacted couples.
Sixty-two percent of the 6,507 couples were contacted and 58% of these responded to the postal questionnaire. Contacted couples were more likely to have had a child during IVF treatment than non-contactable couples, and the same was true of respondents compared with non-respondents. Demographic and medical characteristics were both associated with probability of contact and probability of response. After adjustment, having a live birth during IVF treatment remained associated with both probabilities, and more strongly with probability of response. Having a child during IVF treatment was a major factor impacting on participation rate.
Non-response as well as non-contact were linked to the outcome of interest, i.e. long-term parenthood success of infertile couples. Our study illustrates that an a priori hypothesis may be too simplistic and may underestimate potential bias. In the context of growing use of analytical methods that take attrition into account (such as multiple imputation), we need to better understand the mechanisms that underlie attrition in order to choose the most appropriate method.
PMCID: PMC3489673  PMID: 22824369
Infertility; IVF; Postal survey; Response rate
15.  Lifestyle surveys--the complete answer? 
STUDY OBJECTIVES: These were as follows: to study incompleteness of data, herein called item non-response, generated by a self completion questionnaire; to identify the characteristics of item non-responders and the types of questions liable to high item non-response rates; and to discuss possible reasons for item non-response. DESIGN: Item non-response patterns in 12,307 responders (62%) to a representative postal survey based on a stratified sample drawn from family health services authorities' (FHSA) registers were investigated. MAIN OUTCOME MEASURES: Data were analysed for item non-response in three groups depending on when the questionnaire was returned (wave analysis). The overall completion rate of the questionnaire was examined and the natural logarithm of the proportion of completed questions was used as an outcome variable in multiple regression analysis. Item nonresponse to key questions and questions of different types was examined. RESULTS: Wave analysis: the overall completion rate of the questionnaire was 86% in questionnaires returned before the first reminder and 83%-84% in those sent back after subsequent reminders. Overall pattern of item non-response; respondents failed to complete a mean of 15% and a median of 10% of the questionnaire. All questions in the questionnaire had some item non-response, ranging from 1% to 85%. Completion rates were associated with gender, age, indicators of lower socioeconomic status, and general health status. Individual questions: particular types of questions were liable to have higher item non-response, for example, linked binary questions. CONCLUSIONS: Item non-response in population postal surveys is likely to present problems in the interpretation of data by introducing bias additional to that of total non-response. Item non-response does not increase greatly with later returns, suggesting that the quality of data across responses generated by two reminders is similar. There are obstacles to reducing item non-response, such as respondent error or socioeconomic and health characteristics of the general population, that cannot be totally overcome. However, the evidence that individuals tend to complete only options within questions that apply to them and their positive behaviour is useful information for those designing questionnaires and interpreting survey data.
PMCID: PMC1060409  PMID: 9135788
16.  Can clinicians benefit from patient satisfaction surveys? Evaluating the NSF for Older People, 2005–2006 
A transformation of healthcare is underway, from a sellers' market to a consumers' market, where the satisfaction of the patient's needs is part of the definition of quality. Patient satisfaction surveys are widely used to judge service quality, but clinicians are sceptical about them because they are too often poorly designed measures that do not lead to improvements in the quality of care.
To explore the use of patient satisfaction survey data in identifying problems with the provision of inpatient care for older people.
A case study using secondary analysis of postal survey data about older people's experiences of health and social care services, obtained during the evaluation of the National Service Framework for Older People in 2005–2006. The survey asked about experiences of inpatient care and of discharge from hospital, and sought perceptions of the avoidability of the admission.
Settings and participants
A total of 4170 people aged 50 years and over returned a postal questionnaire in six local authority areas of England. Responses from 584 who had experienced a recent overnight stay in hospital are reported and discussed.
The response rate was 35%, ranging from 26% to 44% in the six areas surveyed. The great majority of those who had recent direct experience of inpatient care reported that they had been engaged in decision-making, that staff promoted their independence and maintained their dignity. There were widespread examples, however, of the opposite experiences. Discharge from hospital was problematic for about one-third of survey respondents with this experience, and there were different accounts of poorly managed discharges from all areas.
Case studies using local survey data can be used as formative assessments of services. The response rate to the survey and the likelihood of responder bias mean that patient satisfaction survey data of this sort cannot be used to judge or compare services in a summative way, but can highlight areas where remedial action is needed. Small-scale local surveys may seem to lack the robustness of larger studies, but do identify similar areas of concern. Commissioners and clinicians could use the findings of such surveys to inform dialogues about the quality of hospital care for older people.
PMCID: PMC2625387  PMID: 19092030
17.  Telephone versus postal surveys of general practitioners: methodological considerations. 
BACKGROUND. High response rates to surveys help to maintain the representativeness of the sample. AIM. In the course of a wider investigation into counselling services within general practice it was decided to assess the feasibility of increasing the response rate by telephone follow up of non-respondents to a postal survey. METHOD. A postal survey was undertaken of a random sample of 1732 general practitioners followed by telephone administration of the questionnaire to non-respondents. The identical questionnaire was administered by telephone to a separate random sample of 206 general practitioners. RESULTS. Of 1732 general practitioners first approached by mail, 1683 were still in post of whom 881 (52%) completed the postal questionnaire and a further 494 (29%) the telephone interview. Of 206 general practitioners first contacted by telephone, 197 were still in post of whom 167 (85%) completed interviews. Compared with doctors first approached by mail, those first approached by telephone were significantly more likely to report having a partner with a special interest in psychiatry (P < 0.01); and a general practitioner, practice nurse or health visitor who worked as a counsellor (P < 0.01 in each case). A comparison of doctors first approached by telephone with those who completed telephone interviews after failing to respond to the postal questionnaire showed that postal non-respondents were significantly less likely to report having a general practitioner, practice nurse, health visitor or community psychiatric nurse who worked as a counsellor (P < 0.01 in each case). CONCLUSION. These findings suggest that non-response to the postal survey was associated with lack of activity in the study area. Telephone administration of questionnaires to postal non-respondents increased response rates to above 80% but, as telephone administration enhanced the reporting of counsellors, a social desirability bias may have been introduced.
PMCID: PMC1238925  PMID: 8068375
18.  Impact of a postcard versus a questionnaire as a first reminder in a postal lifestyle survey. 
STUDY OBJECTIVE--The study aimed to consider the impact of two different types of reminder on response rates and costs in a postal survey. DESIGN--The study was a cross sectional survey. A self-completion lifestyle questionnaire was used. Those who did not respond after the initial mailing were randomly allocated to receive either a postcard or questionnaire as a first reminder. All outstanding non-responders received a questionnaire as a second reminder. SUBJECTS--A representative sample of 698 adults aged 16-70 was used, drawn from a family health services authority register. MAIN RESULTS--Postcard reminders were as effective as questionnaire reminders in increasing response whether one or two reminders are sent. The costs per response were calculated. Two questionnaires as reminders were found to be 1.7 times more expensive than a postcard plus questionnaire. Including the initial mailing, the cost per response using all questionnaires was 1.3 times the cost when a postcard was used for the first reminder. CONCLUSIONS--To increase the response to a postal survey effectively and economically, two reminders should be sent--first a postcard and then a questionnaire.
PMCID: PMC1059805  PMID: 8228774
19.  Depersonalised doctors: a cross-sectional study of 564 doctors, 760 consultations and 1876 patient reports in UK general practice 
BMJ Open  2012;2(1):e000274.
The objectives of this study were to assess burnout in a sample of general practitioners (GPs), to determine factors associated with depersonalisation and to investigate its impact on doctors' consultations with patients.
Cross-sectional, postal survey of GPs using the Maslach Burnout Inventory (MBI). Patient survey and tape-recording of consultations for a subsample of respondents stratified by their MBI scores, gender and duration of General Medical Council registration.
UK general practice.
GPs within NHS Essex.
Primary and secondary outcome measures
Scores on MBI subscales (depersonalisation, emotional exhaustion, personal accomplishment); scores on Doctors' Interpersonal Skills Questionnaire and patient-centredness scores attributed to tape-recorded consultations by independent observers.
In the postal survey, 564/789 (71%) GPs completed the MBI. High levels of emotional exhaustion (261/564 doctors, 46%) and depersonalisation (237 doctors, 42%) and low levels of personal accomplishment (190 doctors, 34%) were reported. Depersonalisation scores were related to characteristics of the doctor and the practice. Male doctors reported significantly higher (p<0.001) depersonalisation than female doctors. Doctors registered with the General Medical Council under 20 years had significantly higher (p=0.005) depersonalisation scores than those registered for longer. Doctors in group practices had significantly higher (p=0.001) depersonalisation scores than single-handed practitioners. Thirty-eight doctors agreed to complete the patient survey (n=1876 patients) and audio-record consultations (n=760 consultations). Depersonalised doctors were significantly more likely (p=0.03) to consult with patients who reported seeing their ‘usual doctor’. There were no significant associations between doctors' depersonalisation and their patient-rated interpersonal skills or observed patient-centredness.
This is the largest number of doctors completing the MBI with the highest levels of depersonalisation reported. Despite experiencing substantial depersonalisation, doctors' feelings of burnout were not detected by patients or independent observers. Such levels of burnout are, however, worrying and imply a need for action by doctors themselves, their medical colleagues, professional bodies, healthcare organisations and the Department of Health.
Article summary
Article focus
A cross-sectional survey was designed to assess levels of burnout in a census sample of GPs in Essex, UK, and to determine which doctor- or practice-related variables predicted higher levels of burnout.
In the substudy, patients rated the interpersonal skills of their doctor and independent observers assessed the degree of patient-centredness in a sample of the doctors' audio-taped consultations.
Key messages
High levels of burnout were reported in the census survey—46% doctors reported emotional exhaustion, 42% reported depersonalisation and 34% reported low levels of personal accomplishment.
Doctors' depersonalisation scores could be predicted by a range of variables relating to the individual doctor and their practice, but higher depersonalisation scores were not associated with poorer patient ratings of the doctors' interpersonal skills or a reduction in the patient-centredness of their consultations.
While the professional practice and patient-centredness of consultations of the GPs in this study were not affected by feelings of burnout, there is a need to offer help and support for doctors who are experiencing this.
Strengths and limitations of this study
A high response rate (71%) was achieved in the census sample of GPs completing the MBI and a subsample of 38 doctors who satisfied the predetermined sample stratification consented to further assessment (patient survey and audio-taping of consultations).
The study was, however, limited to one county in the UK and thus cannot be extrapolated to other parts of the UK.
There was a differential response rate by the gender of the participant. Male doctors who were registered with the General Medical Council for >20 years were less likely to respond to the survey than their female counterparts.
PMCID: PMC3274717  PMID: 22300669
20.  A selective follow-up study on a public health survey 
Background: The non-response rates in surveys are increasing which is problematic as it means that a progressively smaller proportion of the population represents the majority, and it is uncertain how health survey results are affected. This follow-up was performed on the non-responders to the postal questionnaire in the public health survey Life and Health, conducted in Örebro County Council, Sweden, where large differences in response rates had been found between different socio-demographic groups and geographical areas. The main objective was to analyse non-response bias regarding self-rated health. Methods: This follow-up study was conducted as a census to all non-responders in the area that had the lowest response rate and, in one other geographical area used as a control. It was carried out by telephone interviews, 49.3% (580 individuals) answered the follow-up. The outcome variable was self-rated health, a main variable in public health surveys. Differences in response patterns between responders and initial non-responders were approximated by prevalences with confidence intervals and adjusted odds ratios. Results: Poor health was more common in the initial non-response group than among the responders, even with consideration given to sex, age, country of birth and education. However, good health was equally common among responders and initial non-responders. Conclusions: Public health surveys can be biased due to certain groups being under-represented or not represented at all. For this reason, in repeated public health surveys, we recommend selective follow-ups of such groups at regular intervals.
PMCID: PMC3553586  PMID: 22253457
21.  Investigating non-response bias in a survey of disablement in the community: implications for survey methodology. 
STUDY OBJECTIVE--The aim was to investigate the pattern of age specific non-response bias in a two phase survey of disablement in the community. It seeks to examine patterns of response in different age groups to a household based postal questionnaire, and the implication of such trends for the estimation of prevalence of reported dependence. It also looks at the effect that the readiness to respond during the first phase postal questionnaire had on participation in the interview based second phase of the study. DESIGN AND SETTING--A two stage survey of disablement in the population was undertaken. A first phase postal questionnaire was sent to 25,168 households in Calderdale, West Yorkshire, England, to ascertain the prevalence of physical disability. The second phase comprised in depth interviews with a sample of individuals identified in the first phase as being disabled. RESPONDENTS--A total of 21,889 postal questionnaires were returned (87%) representing households containing 42,826 people aged 16 years and over. A disproportionately stratified random sample of 950 respondents reporting disability was taken for the second phase. Of these 891 were still available, and 838 (94%) were interviewed. MEASUREMENTS AND MAIN RESULTS--A study of the timing of response to a postal questionnaire showed that patterns differed for different age groups. The estimated prevalence of those aged 65 years and over who were dependent was steady over time whereas for those in the 16-64 age range the estimated prevalence fell as the survey progressed, indicating a tendency for those who were dependent to respond sooner. Examination of the relationship of responses at phase 1 and phase 2 showed that response to invitation to interview was much less in those who had responded later, and presumably more reluctantly, in the first phase. CONCLUSIONS--These findings raise questions about how different patterns of response might be indicative of bias which could differentially affect final age specific prevalence estimates. They also have methodological implications for the follow up of reluctant responders both to increase the response rate and to secure cooperation in the second phase of a two phase survey.
PMCID: PMC1060767  PMID: 1836811
22.  Gift Card Incentives and Non-Response Bias in a Survey of Vaccine Providers: The Role of Geographic and Demographic Factors 
PLoS ONE  2011;6(11):e28108.
This study investigates the effects of non-response bias in a 2010 postal survey assessing experiences with H1N1 influenza vaccine administration among a diverse sample of providers (N = 765) in Washington state. Though we garnered a high response rate (80.9%) by using evidence-based survey design elements, including intensive follow-up and a gift card incentive from Target, non-response bias could exist if there were differences between respondents and non-respondents. We investigated differences between the two groups for seven variables: road distance to the nearest Target store, practice type, previous administration of vaccines, region, urbanicity, size of practice, and Vaccines for Children (VFC) program enrollment. We also examined the effect of non-response bias on survey estimates. Statistically significant differences between respondents and non-respondents were found for four variables: miles to the nearest Target store, type of medical practice, whether the practice routinely administered additional vaccines besides H1N1, and urbanicity. Practices were more likely to respond if they were from a small town or rural area (OR = 7.68, 95% CI = 1.44−40.88), were a non-traditional vaccine provider type (OR = 2.08, 95% CI = 1.06−4.08) or a pediatric provider type (OR = 4.03, 95% CI = 1.36−11.96), or administered additional vaccines besides H1N1 (OR = 1.80, 95% CI = 1.03−3.15). Of particular interest, for each ten mile increase in road distance from the nearest Target store, the likelihood of provider response decreased (OR = 0.73, 95% CI = 0.60−0.89). Of those variables associated with response, only small town or rural practice location was associated with a survey estimate of interest, suggesting that non-response bias had a minimal effect on survey estimates. These findings show that gift card incentives alongside survey design elements and follow-up can achieve high response rates. However, there is evidence that practices farther from the nearest place to redeem gift cards may be less likely to respond to the survey.
PMCID: PMC3223226  PMID: 22132224
23.  A randomised trial and economic evaluation of the effect of response mode on response rate, response bias, and item non-response in a survey of doctors 
Surveys of doctors are an important data collection method in health services research. Ways to improve response rates, minimise survey response bias and item non-response, within a given budget, have not previously been addressed in the same study. The aim of this paper is to compare the effects and costs of three different modes of survey administration in a national survey of doctors.
A stratified random sample of 4.9% (2,702/54,160) of doctors undertaking clinical practice was drawn from a national directory of all doctors in Australia. Stratification was by four doctor types: general practitioners, specialists, specialists-in-training, and hospital non-specialists, and by six rural/remote categories. A three-arm parallel trial design with equal randomisation across arms was used. Doctors were randomly allocated to: online questionnaire (902); simultaneous mixed mode (a paper questionnaire and login details sent together) (900); or, sequential mixed mode (online followed by a paper questionnaire with the reminder) (900). Analysis was by intention to treat, as within each primary mode, doctors could choose either paper or online. Primary outcome measures were response rate, survey response bias, item non-response, and cost.
The online mode had a response rate 12.95%, followed by the simultaneous mixed mode with 19.7%, and the sequential mixed mode with 20.7%. After adjusting for observed differences between the groups, the online mode had a 7 percentage point lower response rate compared to the simultaneous mixed mode, and a 7.7 percentage point lower response rate compared to sequential mixed mode. The difference in response rate between the sequential and simultaneous modes was not statistically significant. Both mixed modes showed evidence of response bias, whilst the characteristics of online respondents were similar to the population. However, the online mode had a higher rate of item non-response compared to both mixed modes. The total cost of the online survey was 38% lower than simultaneous mixed mode and 22% lower than sequential mixed mode. The cost of the sequential mixed mode was 14% lower than simultaneous mixed mode. Compared to the online mode, the sequential mixed mode was the most cost-effective, although exhibiting some evidence of response bias.
Decisions on which survey mode to use depend on response rates, response bias, item non-response and costs. The sequential mixed mode appears to be the most cost-effective mode of survey administration for surveys of the population of doctors, if one is prepared to accept a degree of response bias. Online surveys are not yet suitable to be used exclusively for surveys of the doctor population.
PMCID: PMC3231767  PMID: 21888678
24.  Towards socially inclusive research: An evaluation of telephone questionnaire administration in a multilingual population 
Missing data may bias the results of clinical trials and other studies. This study describes the response rate, questionnaire responses and financial costs associated with offering participants from a multilingual population the option to complete questionnaires over the telephone.
Design: Before and after study of two methods of questionnaire completion. Participants and Setting: Seven hundred and sixty five pregnant women from 25 general practices in two UK inner city Primary Care Trusts (PCTs) taking part in a cluster randomised controlled trial of offering antenatal sickle cell and thalassaemia screening in primary care. Two hundred and four participants did not speak English. Sixty one women were offered postal questionnaire completion only and 714 women were offered a choice of telephone or postal questionnaire completion.
Outcome measures: (i) Proportion of completed questionnaires, (ii) attitude and knowledge responses obtained from a questionnaire assessing informed choice.
The response rate from women offered postal completion was 26% compared with 67% for women offered a choice of telephone or postal completion (41% difference 95% CI Diff 30 to 52). For non-English speakers offered a choice of completion methods the response rate was 56% compared with 71% for English speakers (95% CI Diff 7 to 23). No difference was found for knowledge by completion method, but telephone completion was associated with more positive attitude classifications than postal completion (87 vs 96%, 95% CI diff 0.006 to 15). Compared with postal administration the additional costs associated with telephone administration were £3.90 per questionnaire for English speakers and £71.60 per questionnaire for non English speakers.
Studies requiring data to be collected by questionnaire may obtain higher response rates from both English and non-English speakers when a choice of telephone or postal administration (and where necessary, an interpreter)is offered compared to offering postal administration only. This approach will, however, incur additional research costs and uncertainty remains about the equivalence of responses obtained from the two methods.
PMCID: PMC2270862  PMID: 18237377
25.  The effect of cash and other financial inducements on the response rate of general practitioners in a national postal study. 
BACKGROUND: Low response rates are acknowledged as a potential source of bias in survey results. Response rates are a particular problem in surveys of GPs. Thus, the methods used to encourage response to mailed surveys and the influence of inducements in maximizing response rates are fundamental issues to be examined when addressing the problem of response bias. AIM: To increase the overall response rate to a national study of GPs and to explore the effects of financial and non-financial inducements on response rates. METHODS: Two mailing waves of a postal questionnaire to a 20% random sample of all GPs in England and Wales had achieved a 33% response rate. For the third mailing wave, the non-responding GPs were then divided into a control group, a group who were offered a donation to charity to complete the questionnaire and a group who were offered cash. The charity and cash groups were further subdivided into 5 pounds and 10 pounds groups to assess the effect of the size of the inducement offered. For the control group, a fourth wave was sent the offer of a 5 pounds or 10 pounds incentive. RESULTS: Response was positively affected by the offer of an inducement. Cash, however, had a more substantial effect than the offer of a donation to charity. Older GPs were less likely to participate overall, whereas male GPs were more likely to respond to a cash inducement. Doctors who had seen more patients were less likely to reply earlier and were more likely to respond to the offer of cash. CONCLUSIONS: Primary care is going through many changes, some of which have increased the workload of the GP. It may now be that, to achieve the response rates needed to validate policy-related research, the offer of inducements will become a necessary part of the research process.
PMCID: PMC1312912  PMID: 9101691

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