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1.  Measuring Client Experiences in Maternity Care under Change: Development of a Questionnaire Based on the WHO Responsiveness Model 
PLoS ONE  2015;10(2):e0117031.
Background
Maternity care is an integrated care process, which consists of different services, involves different professionals and covers different time windows. To measure performance of maternity care based on clients' experiences, we developed and validated a questionnaire.
Methods and Findings
We used the 8-domain WHO Responsiveness model, and previous materials to develop a self-report questionnaire. A dual study design was used for development and validation. Content validity of the ReproQ-version-0 was determined through structured interviews with 11 pregnant women (≥28 weeks), 10 women who recently had given birth (≤12 weeks), and 19 maternity care professionals. Structured interviews established the domain relevance to the women; all items were separately commented on. All Responsiveness domains were judged relevant, with Dignity and Communication ranking highest. Main missing topic was the assigned expertise of the health professional. After first adaptation, construct validity of the ReproQ-version-1 was determined through a web-based survey. Respondents were approached by maternity care organizations with different levels of integration of services of midwives and obstetricians. We sent questionnaires to 605 third trimester pregnant women (response 65%), and 810 women 6 weeks after delivery (response 55%). Construct validity was based on: response patterns; exploratory factor analysis; association of the overall score with a Visual Analogue Scale (VAS), known group comparisons. Median overall ReproQ score was 3.70 (range 1–4) showing good responsiveness. The exploratory factor analysis supported the assumed domain structure and suggested several adaptations. Correlation of the VAS rating and overall ReproQ score (antepartum, postpartum) supported validity (r = 0.56; 0.59, p<0.001 Spearman's correlation coefficient). Pre-stated group comparisons confirmed the expected difference following a good vs. adverse birth outcome. Fully integrated organizations performed slightly better (median = 3.78) than less integrated organizations (median = 3.63; p<0.001). Participation rate of women with a low educational level and/or a non-western origin was low.
Conclusions
The ReproQ appears suitable for assessing quality of maternity care from the clients' perspective. Recruitment of disadvantaged groups requires additional non-digital approaches.
doi:10.1371/journal.pone.0117031
PMCID: PMC4324965  PMID: 25671310
2.  Effectiveness of score card-based antenatal risk selection, care pathways, and multidisciplinary consultation in the Healthy Pregnancy 4 All study (HP4ALL): study protocol for a cluster randomized controlled trial 
Trials  2015;16:8.
Background
Promotion of healthy pregnancies has gained high priority in the Netherlands because of relatively unfavorable perinatal outcomes. In response, a nationwide study, ‘Healthy Pregnancy 4 All’ (HP4ALL), has been initiated. Part of this study involves systematic and broadened antenatal risk assessment (the Risk Assessment substudy). Risk selection in current clinical practice is mainly based on medical risk factors. Despite the increasing evidence for the influence of nonmedical risk factors (social status, lifestyle or ethnicity) on perinatal outcomes, these risk factors remain highly unexposed. Systematic risk selection, combined with customized care pathways to reduce or treat detected risks, and regular and structured consultation between community midwives, gynecologists and other care providers such as social workers, is part of this study.
Methods/Design
Neighborhoods in 14 municipalities with adverse perinatal outcomes above national and municipal averages are selected for participation. The study concerns a cluster randomized controlled trial. Municipalities are randomly allocated to intervention (n = 3,500 pregnant women) and control groups (n = 3,500 pregnant women). The intervention consists of systematic risk selection with the Rotterdam Reproductive Risk Reduction (R4U) score card in pregnant women at the booking visit, and referral to corresponding care pathways. A risk score, based on weighed risk factors derived from the R4U, above a predefined threshold determines structured multidisciplinary consultation. Primary outcomes of this trial are dysmaturity (birth weight < p10), prematurity (birth <37 weeks), and efficacy of implementation.
Discussion
The ‘HP4ALL’ study introduces a systematic approach in antenatal health care that may improve perinatal outcomes and, thereby, affect future health status of a new generation in the Netherlands.
Trial registration
Dutch Trial Registry ( NTR-3367) on 20 March 2012.
Electronic supplementary material
The online version of this article (doi:10.1186/1745-6215-16-8) contains supplementary material, which is available to authorized users.
doi:10.1186/1745-6215-16-8
PMCID: PMC4326478  PMID: 25559202
Pregnancy; Antenatal healthcare; Care pathway; Collaboration; Risk assessment
3.  Validity of a questionnaire measuring the world health organization concept of health system responsiveness with respect to perinatal services in the dutch obstetric care system 
Background
The concept of responsiveness, introduced by the World Health Organization (WHO), addresses non-clinical aspects of health service quality that are relevant regardless of provider, country, health system or health condition. Responsiveness refers to “aspects related to the way individuals are treated and the environment in which they are treated” during health system interactions. This paper assesses the psychometric properties of a newly developed responsiveness questionnaire dedicated to evaluating maternal experiences of perinatal care services, called the Responsiveness in Perinatal and Obstetric Health Care Questionnaire (ReproQ), using the eight-domain WHO concept.
Methods
The ReproQ was developed between October 2009 and February 2010 by adapting the WHO Responsiveness Questionnaire items to the perinatal care context. The psychometric properties of feasibility, construct validity, and discriminative validity were empirically assessed in a sample of Dutch women two weeks post partum.
Results
A total of 171 women consented to participation. Feasibility: the interviews lasted between 20 and 40 minutes and the overall missing rate was 8%. Construct validity: mean Cronbach’s alphas for the antenatal, birth and postpartum phase were: 0.73 (range 0.57-0.82), 0.84 (range 0.66-0.92), and 0.87 (range 0.62-0.95) respectively. The item-own scale correlations within all phases were considerably higher than most of the item-other scale correlations. Within the antenatal care, birth care and post partum phases, the eight factors explained 69%, 69%, and 76% of variance respectively. Discriminative validity: overall responsiveness mean sum scores were higher for women whose children were not admitted. This confirmed the hypothesis that dissatisfaction with health outcomes is transferred to their judgement on responsiveness of the perinatal services.
Conclusions
The ReproQ interview-based questionnaire demonstrated satisfactory psychometric properties to describe the quality of perinatal care in the Netherlands, with the potential to discriminate between different levels of quality of care. In view of the relatively small sample, further testing and research is recommended.
Electronic supplementary material
The online version of this article (doi:10.1186/s12913-014-0622-1) contains supplementary material, which is available to authorized users.
doi:10.1186/s12913-014-0622-1
PMCID: PMC4265356  PMID: 25465053
Responsiveness; Psychometric properties; Quality of care; Perinatal care
4.  Design and outline of the Healthy Pregnancy 4 All study 
Background
Promotion of healthy pregnancies has gained high priority in the Netherlands because of the relatively unfavourable perinatal health outcomes. In response a nationwide study Healthy Pregnancy 4 All was initiated. This study combines public health and epidemiologic research to evaluate the effectiveness of two obstetric interventions before and during pregnancy: (1) programmatic preconception care (PCC) and (2) systematic antenatal risk assessment (including both medical and non-medical risk factors) followed by patient-tailored multidisciplinary care pathways. In this paper we present an overview of the study setting and outlines. We describe the selection of geographical areas and introduce the design and outline of the preconception care and the antenatal risk assessment studies.
Methods/design
A thorough analysis was performed to identify geographical areas in which adverse perinatal outcomes were high. These areas were regarded as eligible for either or both sub-studies as we hypothesised studies to have maximal effect there. This selection of municipalities was based on multiple criteria relevant to either the preconception care intervention or the antenatal risk assessment intervention, or to both. The preconception care intervention was designed as a prospective community-based cohort study. The antenatal risk assessment intervention was designed as a cluster randomised controlled trial – where municipalities are randomly allocated to intervention and control.
Discussion
Optimal linkage is sought between curative and preventive care, public health, government, and social welfare organisations. To our knowledge, this is the first study in which these elements are combined.
doi:10.1186/1471-2393-14-253
PMCID: PMC4133626  PMID: 25080942
Cohort study; Randomized controlled trial; Preconception care; Antenatal care; Public health; Epidemiology; Pregnancy; Neighbourhood; Care pathway
5.  Posttraumatic stress symptoms and health-related quality of life: a two year follow up study of injury treated at the emergency department 
BMC Psychiatry  2012;12:1.
Background
Among injury victims relatively high prevalence rates of posttraumatic stress disorder (PTSD) have been found. PTSD is associated with functional impairments and decreased health-related quality of life (HRQoL). Previous studies that addressed the latter were restricted to injuries at the higher end of the severity spectrum. This study examined the association between PTSD symptoms and health-related quality of life (HRQoL) in a comprehensive population of injury patients of all severity levels and external causes.
Methods
We conducted a self-assessment survey which included items regarding demographics of the patient, accident type, sustained injuries, EuroQol health classification system (EQ-5D) and Health Utilities Index (HUI) to measure functional outcome and HRQoL, and the Impact of Event Scale (IES) to measure PTSD symptoms. An IES-score of 35 or higher was used as indication for the presence of PTSD. The survey was completed by 1,781 injury patients two years after they were treated at the Emergency Department (ED), followed by either hospital admission or direct discharge to the home environment.
Results
Symptoms indicative of PTSD were associated with more problems on all EQ-5D and HUI3 domains of functional outcome and a considerable utility loss in both hospitalized (0.23-0.24) and non-hospitalized (0.32-0.33) patients. Differences in reported problems between patients with IES scores higher or lower than 35 were largest for EQ-5D health domains pain/discomfort (82% versus 28%) and anxiety/depression (53% versus 11%) and HUI domains emotion (92% versus 33%) and pain (84% versus 38%). After adjusting for potential confounders, PTSD remained strongly associated with adverse HRQoL.
Conclusions
Among patients treated at an ED posttraumatic stress symptoms indicative of PTSD were associated with a considerable decrease in HRQoL in both hospitalized and non-hospitalized patients. PTSD symptoms may therefore raise a major barrier for full recovery of injury patients of even minor levels of severity.
doi:10.1186/1471-244X-12-1
PMCID: PMC3276433  PMID: 22230388
posttraumatic stress disorder; injury; functional outcome; quality of life
6.  Obstetrical outcome valuations by patients, professionals, and laypersons: differences within and between groups using three valuation methods 
Background
Decision-making can be based on treatment preferences of the patient, the doctor, or by guidelines based on lay people's preferences. We compared valuations assigned by three groups: patients, obstetrical care professionals, and laypersons, for health states involving both mother and (unborn) child. Our aim was to compare the valuations of different groups using different valuation methods and complex obstetric health outcome vignettes that involve both maternal and neonatal outcomes.
Methods
Patients (n = 24), professionals (n = 30), and laypersons (n = 27) valued the vignettes using three valuation methods: visual analogue scale (VAS), time trade-off (TTO), and discrete choice experimentation (DCE). Each vignette covered five health attributes: maternal health ante partum, time between diagnosis and delivery, process of delivery, maternal outcome, and neonatal outcome. We used feasibility questionnaires, Generalization theory, test-retest reliability and within-group reliability to compare the valuation patterns between groups and methods. We assessed relative weights from each valuation method to test for consistency across groups.
Results
Test-retest reliability was equal across groups, but different across methods: highest for VAS (ICC = 0.61-0.73), intermediate for TTO (ICC = 0.24-0.74) and lowest for DCE (kappa = 0.15-0.37). Within-group reliability was highest in all groups with VAS (ICC = 0.70-0.73), intermediate with DCE (kappa = 0.56-0.76) and lowest with TTO (ICC = 0.20-0.66). Effects of groups were smaller than effects of methods. Differences between groups were largest for severe health states.
Conclusion
Based on our results, decision making among laypersons should use TTO or DCE; patients should use VAS or TTO.
doi:10.1186/1471-2393-11-93
PMCID: PMC3226638  PMID: 22078302
health outcome valuation; preference; vignettes; psychometrics; pregnancy; obstetrics
7.  Contribution of Primary Pelvic Organ Prolapse to Micturition and Defecation Symptoms 
Objective. To investigate the contribution of Pelvic Organ Prolapse (POP) to micturition and defecation symptoms. Method. Cross-sectional study including 64 women presenting with POP symptoms and 50 controls without POP complaints. Subjects were evaluated using POP-Quantification system, Urinary Distress Inventory, and Defecation Distress Inventory. The MOS SF-36 health survey and the Center for Epidemiological Studies Depression scale were used to measure self-perceived health status and depressive symptoms, respectively. Results. POP in terms of POP-Q had a moderate impact on the symptom observing vaginal protrusion (explained variance 0.31). It contributed modestly to obstructive voiding and overactive bladder symptoms (explained variance 0.09, resp., 0.14) but not to urinary incontinence. Constipation was more likely explained by clinical depression than by pelvic floor defects (explained variance 0.13, resp., 0.05). Conclusion. Stage of POP and specific prolapse symptoms are associated but such a strong association does not exist between POP and micturition or defecation symptoms.
doi:10.1155/2012/798035
PMCID: PMC3182371  PMID: 21969831
8.  The effect of comorbidity on health-related quality of life for injury patients in the first year following injury: comparison of three comorbidity adjustment approaches 
Background
Three approaches exist to deal with the impact of comorbidity in burden of disease studies - the maximum limit approach, the additive approach, and the multiplicative approach. The aim of this study was to compare the three comorbidity approaches in patients with temporary injury consequences as well as comorbid chronic conditions with nontrivial health impacts.
Methods
Disability weights were assessed using data from the EQ-5D instrument developed by the EuroQol Group and derived from a postal survey among 2,295 injury patients at 2.5 and 9 months after being treated at an emergency department. We compared the observed and predicted EQ-5D disability weights in comorbid cases using data from injury patients with and without comorbidity who were restored from their injuries at 9 months follow-up. The predicted disability weights were calculated using the maximum limit approach, additive approach, and multiplicative approach. The intraclass correlation coefficient (ICC) was used to test whether the values of the observed disability weights and the three model-predicted disability weights were correlated.
Results
The EQ-5D disability weight of injury patients increased significantly with the number of comorbid diseases. The ICCs of the additive, multiplicative, and maximum limit models were 0.817, 0.778, and 0.674, respectively. Although the 95% confidence intervals of the ICCs of the three models overlap, the maximum limit model seems to fit less well than the additive and multiplicative models. For mild to moderate chronic disease (disability weight below 0.21), the association between predicted and observed disability weights was low.
Conclusions
Comorbidity has a high impact on disability measured with EQ-5D. Ignoring the effect of comorbidity restricts the use of the burden of disease concept in multimorbid populations. Gains from health care or interventions may be easily overestimated if a substantial number of patients suffer from additional conditions. The results of this study found that in accounting for comorbidity effects, all three models showed a strong association between the predicted and observed morbid disability weight, though the maximum limit model seems to fit less well than the additive and multiplicative models. The three models do not fit well in the case of mild to moderate pre-existing disease.
doi:10.1186/1478-7954-9-10
PMCID: PMC3096905  PMID: 21513572
9.  Maternal health-related quality of life after induction of labor or expectant monitoring in pregnancy complicated by intrauterine growth retardation beyond 36 weeks 
Quality of Life Research  2011;20(9):1427-1436.
Objective
Pregnancies complicated by intrauterine growth retardation (IUGR) beyond 36 weeks of gestation are at increased risk of neonatal morbidity and mortality. Optimal treatment in IUGR at term is highly debated. Results from the multicenter DIGITAT (Disproportionate Intrauterine Growth Intervention Trial At Term) trial show that induction of labor and expectant monitoring result in equal neonatal and maternal outcomes for comparable cesarean section rates. We report the maternal health-related quality of life (HR-QoL) that was measured alongside the trial at several points in time.
Methods
Both randomized and non-randomized women were asked to participate in the HR-QoL study. Women were asked to fill out written validated questionnaires, covering background characteristics, condition-specific issues and the Short Form (SF-36), European Quality of Life (EuroQoL 6D3L), Hospital Anxiety and Depression scale (HADS), and Symptom Check List (SCL-90) at baseline, 6 weeks postpartum and 6 months postpartum. We compared the difference scores of all summary measures between the two management strategies by ANOVA. A repeated measures multivariate mixed model was defined to assess the effect of the management strategies on the physical (PCS) and mental (MCS) components of the SF-36. Analysis was by intention to treat.
Results
We analyzed data of 361 randomized and 198 non-randomized patients. There were no clinically relevant differences between the treatments at 6 weeks or 6 months postpartum on any summary measures; e.g., on the SF-36 (PCS: P = .09; MCS: P = .48). The PCS and the MCS were below norm values at inclusion. The PCS improved over time but stayed below norm values at 6 months, while the MCS did not improve.
Conclusion
In pregnancies complicated by IUGR beyond 36 weeks, induction of labor does not affect the long-term maternal quality of life.
doi:10.1007/s11136-011-9891-x
PMCID: PMC3195683  PMID: 21468753
Intrauterine growth retardation; Small for gestational age; Quality of life; Induction of labor; Expectant management
10.  Obtaining insurance after DNA diagnostics: a survey among hypertrophic cardiomyopathy mutation carriers 
Hypertrophic cardiomyopathy (HCM) is a common hereditary heart disease associated with increased mortality. Disclosure of DNA test results may have social implications such as low access to insurance. In the Netherlands, insurance companies are restricted in the use of genetic information of their clients by the Medical Examination Act. A cross-sectional survey was used to assess the frequency and type of problems encountered by HCM mutation carriers applying for insurance, and associations with carriers' characteristics. The response rate was 86% (228/264). A total of 66 carriers (29%) applied for insurance of whom 39 reported problems (59%) during an average follow-up of 3 years since the DNA test result. More problems were encountered by carriers with manifest disease (P<0.001) and carriers with symptoms of HCM (P=0.049). Carriers identified after predictive DNA testing less frequently experienced problems (P=0.002). Three carriers without manifest HCM reported problems (5% of applicants). Frequently reported problems were higher premium (72%), grant access to medical records (62%), and complete rejection (33%). In conclusion, HCM mutation carriers frequently encounter problems when applying for insurances, often in the case of manifest disease, but the risk assessment of insurance companies is largely justified. Still, 5% of carriers encounter potentially unjustified problems, indicating the necessity to monitor the application of the existing laws and regulations by insurance companies and to educate counselees on the implications of these laws and regulations.
doi:10.1038/ejhg.2009.145
PMCID: PMC2987186  PMID: 19672285
hypertrophic cardiomyopathy; insurance; genetic testing
11.  Individual accumulation of heterogeneous risks explains perinatal inequalities within deprived neighbourhoods 
European Journal of Epidemiology  2011;26(2):165-180.
Dutch’ figures on perinatal mortality and morbidity are poor compared to EU-standards. Considerable within-country differences have been reported too, with decreased perinatal health in deprived urban areas. We investigated associations between perinatal risk factors and adverse perinatal outcomes in 7,359 pregnant women participating in population-based prospective cohort study, to establish the independent role, if any, for living within a deprived urban neighbourhood. Main outcome measures included perinatal death, intrauterine growth restriction (IUGR), prematurity, congenital malformations, Apgar at 5 min < 7, and pre-eclampsia. Information regarding individual risk factors was obtained from questionnaires, physical examinations, ultrasounds, biological samples, and medical records. The dichotomous Dutch deprivation indicator was additionally used to test for unexplained deprived urban area effects. Pregnancies from a deprived neighbourhood had an increased risk for perinatal death (RR 1.8, 95% CI [1.1; 3.1]). IUGR, prematurity, Apgar at 5 min < 7, and pre-eclampsia also showed higher prevalences (P < 0.05). Residing within a deprived neighbourhood was associated with increased prevalence of all measured risk factors. Regression analysis showed that the observed neighbourhood related differences in perinatal outcomes could be attributed to the increased risk factor prevalence only, without a separated role for living within a deprived neighbourhood. Women from a deprived neighbourhood had significantly more ‘possibly avoidable’ risk factors. To conclude, women from a socioeconomically deprived neighbourhood are at an increased risk for adverse pregnancy outcomes. Differences regarding possibly avoidable risk factors imply that preventive strategies may prove effective.
doi:10.1007/s10654-010-9542-5
PMCID: PMC3043261  PMID: 21203801
Perinatal mortality; Prevention; Residence characteristics; Pregnancy; Risk factors
12.  Long term costs and effects of reducing the number of twin pregnancies in IVF by single embryo transfer: the TwinSing study 
BMC Pediatrics  2010;10:75.
Background
Pregnancies induced by in vitro fertilisation (IVF) often result in twin gestations, which are associated with both maternal and perinatal complications. An effective way to reduce the number of IVF twin pregnancies is to decrease the number of embryos transferred from two to one. The interpretation of current studies is limited because they used live birth as outcome measure and because they applied limited time horizons. So far, research on long-term outcomes of IVF twins and singletons is scarce and inconclusive. The objective of this study is to investigate the short (1-year) and long-term (5 and 18-year) costs and health outcomes of IVF singleton and twin children and to consider these in estimating the cost-effectiveness of single embryo transfer compared with double embryo transfer, from a societal and a healthcare perspective.
Methods/Design
A multi-centre cohort study will be performed, in which IVF singletons and IVF twin children born between 2003 and 2005 of whom parents received IVF treatment in one of the five participating Dutch IVF centres, will be compared. Data collection will focus on children at risk of health problems and children in whom health problems actually occurred. First year of life data will be collected in approximately 1,278 children (619 singletons and 659 twin children). Data up to the fifth year of life will be collected in approximately 488 children (200 singletons and 288 twin children). Outcome measures are health status, health-related quality of life and costs. Data will be obtained from hospital information systems, a parent questionnaire and existing registries. Furthermore, a prognostic model will be developed that reflects the short and long-term costs and health outcomes of IVF singleton and twin children. This model will be linked to a Markov model of the short-term cost-effectiveness of single embryo transfer strategies versus double embryo transfer strategies to enable the calculation of the long-term cost-effectiveness.
Discussion
This is, to our knowledge, the first study that investigates the long-term costs and health outcomes of IVF singleton and twin children and the long-term cost-effectiveness of single embryo transfer strategies versus double embryo transfer strategies.
doi:10.1186/1471-2431-10-75
PMCID: PMC2978208  PMID: 20961411
13.  Regional perinatal mortality differences in the Netherlands; care is the question 
BMC Public Health  2009;9:102.
Background
Perinatal mortality is an important indicator of health. European comparisons of perinatal mortality show an unfavourable position for the Netherlands. Our objective was to study regional variation in perinatal mortality within the Netherlands and to identify possible explanatory factors for the found differences.
Methods
Our study population comprised of all singleton births (904,003) derived from the Netherlands Perinatal Registry for the period 2000–2004. Perinatal mortality including stillbirth from 22+0 weeks gestation and early neonatal death (0–6 days) was our main outcome measure. Differences in perinatal mortality were calculated between 4 distinct geographical regions North-East-South-West. We tried to explain regional differences by adjustment for the demographic factors maternal age, parity and ethnicity and by socio-economic status and urbanisation degree using logistic modelling. In addition, regional differences in mode of delivery and risk selection were analysed as health care factors. Finally, perinatal mortality was analysed among five distinct clinical risk groups based on the mediating risk factors gestational age and congenital anomalies.
Results
Overall perinatal mortality was 10.1 per 1,000 total births over the period 2000–2004. Perinatal mortality was elevated in the northern region (11.2 per 1,000 total births). Perinatal mortality in the eastern, western and southern region was 10.2, 10.1 and 9.6 per 1,000 total births respectively. Adjustment for demographic factors increased the perinatal mortality risk in the northern region (odds ratio 1.20, 95% CI 1.12–1.28, compared to reference western region), subsequent adjustment for socio-economic status and urbanisation explained a small part of the elevated risk (odds ratio 1.11, 95% CI 1.03–1.20). Risk group analysis showed that regional differences were absent among very preterm births (22+0 – 25+6 weeks gestation) and most prominent among births from 32+0 gestation weeks onwards and among children with severe congenital anomalies. Among term births (≥ 37+0 weeks) regional mortality differences were largest for births in women transferred from low to high risk during delivery.
Conclusion
Regional differences in perinatal mortality exist in the Netherlands. These differences could not be explained by demographic or socio-economic factors, however clinical risk group analysis showed indications for a role of health care factors.
doi:10.1186/1471-2458-9-102
PMCID: PMC2674436  PMID: 19366460
14.  Ignoring Dependency between Linking Variables and Its Impact on the Outcome of Probabilistic Record Linkage Studies 
Objectives
This study sought to examine the differences between ignoring (naïve) and incorporating dependency (nonnaïve) among linkage variables on the outcome of a probabilistic record linkage study.
Design and Measurements
We used the outcomes of a previously developed probabilistic linkage procedure for different registries in perinatal care assuming independence among linkage variables. We estimated the impact of ignoring dependency by re-estimating the linkage weights after constructing a variable that combines the outcomes of the comparison of 2 correlated linking variables. The results of the original naïve and the new nonnaïve strategy were systematically compared for 3 scenarios: the empirical dataset using 9 variables, the empirical dataset using 5 variables, and a simulated dataset using 5 variables.
Results
The linking weight for agreement on 2 correlated variables among nonmatches was estimated considerably higher in the naïve strategy than in the nonnaïve strategy (16.87 vs. 13.55). Therefore, ignoring dependency overestimates the amount of identifying information if both correlated variables agree. The impact on the number of pairs that was classified differently with both approaches was modest in the situation in which there were many different linking variables but grew substantially with fewer variables. The simulation study confirmed the results of the empirical study and suggests that the number of misclassifications can increase substantially by ignoring dependency under less favorable linking conditions.
Conclusion
Dependency often exists between linking variables and has the potential to bias the outcome of a linkage study. The nonnaïve approach is a straightforward method for creating linking weights that accommodate dependency. The impact on the number of misclassifications depends on the quality and number of linking variables relative to the number of correlated linking variables.
doi:10.1197/jamia.M2265
PMCID: PMC2528043  PMID: 18579842
15.  Disability Adjusted Life Years and minimal disease: application of a preference-based relevance criterion to rank enteric pathogens 
Background
Burden of disease estimates, which combine mortality and morbidity into a single measure, are used increasingly for priority setting in disease control, prevention and surveillance. However, because there is no clear exclusion criterion for highly prevalent minimal disease in burden of disease studies its application may be restricted. The aim of this study was to apply a newly developed relevance criterion based on preferences of a population panel, and to compare burden of disease estimates of five foodborne pathogens calculated with and without application of this criterion.
Methods
Preferences for twenty health states associated with foodborne disease were obtained from a population panel (n = 107) with the Visual Analogue Scale and the Time Trade-off (TTO) technique. The TTO preferences were used to derive the relevance criterion: if at least 50% of a panel of judges is willing to trade-off time in order to be restored to full health the health state is regarded as relevant, i.e. TTO median is greater than 0. Subsequently, the burden of disease of each of the five foodborne pathogens was calculated both with and without the relevance criterion.
Results
The panel ranked the health states consistently. Of the twenty health states, three did not meet the preference-based relevance criterion. Application of the relevance criterion reduced the burden of disease estimate of all five foodborne pathogens. The reduction was especially significant for norovirus and rotavirus, decreasing with 94% and 78% respectively.
Conclusion
Individual preferences elicited with the TTO from a population panel can be used to empirically derive a relevance criterion for burden of disease estimates. Application of this preference-based relevance criterion results in considerable changes in ranking of foodborne pathogens.
doi:10.1186/1478-7954-6-7
PMCID: PMC2655281  PMID: 19114007
16.  Multiplex ligation-dependent probe amplification versus karyotyping in prenatal diagnosis: the M.A.K.E. study 
Background
In the past 30 years karyotyping was the gold standard for prenatal diagnosis of chromosomal aberrations in the fetus. Traditional karyotyping (TKT) has a high accuracy and reliability. However, it is labor intensive, the results take 14–21 days, the costs are high and unwanted findings such as abnormalities with unknown clinical relevance are not uncommon. These disadvantages challenged the practice of karyotyping. Multiplex ligation-dependent probe amplification (MLPA) is a new molecular genetic technique in prenatal diagnosis. Previous preclinical evidence suggests equivalence of MLPA and traditional karyotyping (TKT) regarding test performance.
Methods/Design
The proposed study is a multicentre diagnostic substitute study among pregnant women, who choose to have amniocentesis for the indication advanced maternal age and/or increased risk following prenatal screening test. In all subjects, both MLPA and karyotyping will be performed on the amniotic fluid sample. The primary outcome is diagnostic accuracy. Secondary outcomes will be maternal quality of life, women's preferences and costs. Analysis will be intention to treat and per protocol analysis. Quality of life analysis will be carried out within the study population. The study aims to include 4500 women.
Discussion
The study results are expected to help decide whether MLPA can replace traditional karyotyping for 'low-risk' pregnancies in terms of diagnostic accuracy, quality of life and women's preferences. This will be the first clinical study to report on all relevant aspects of the potential replacement.
Trial Registration
The protocol is registered in the clinical trial register number ISRCTN47252164
doi:10.1186/1471-2393-8-18
PMCID: PMC2405770  PMID: 18492228
17.  Evaluating the discriminatory power of EQ-5D, HUI2 and HUI3 in a US general population survey using Shannon’s indices 
Quality of Life Research  2007;16(5):895-904.
Objectives
To compare quantitatively the discriminatory power of the EQ-5D, HUI2 and HUI3 in terms of absolute and relative informativity, using Shannon’s indices.
Methods
EQ-5D and HUI2/3 data completed by a sample of the general adult US population (N = 3,691) were used. Five dimensions allowed head-to-head comparison of informativity: Mobility/Ambulation; Anxiety/Depression/Emotion; Pain/Discomfort (EQ-5D; HUI2; HUI3); Self-Care (EQ-5D; HUI2); and Cognition (HUI2; HUI3). Shannon’s index and Shannon’s Evenness index were used to assess absolute and relative informativity, both by dimension and by instrument as a whole.
Results
Absolute informativity was highest for HUI3, with the largest differences in Pain/Discomfort and Cognition. Relative informativity was highest for EQ-5D, with the largest differences in Mobility/Ambulation and Anxiety/Depression/Emotion. Absolute informativity by instrument was consistently highest for HUI3 and lowest for EQ-5D, and relative informativity was highest for EQ-5D and lowest for HUI3.
Discussion
Performance in terms of absolute and relative informativity of the common dimensions of the three instruments varies over dimensions. Several dimensions are suboptimal: Pain/Discomfort (EQ-5D) seems too crude with only 3 levels, and the level descriptions of Ambulation (HUI3) and Self-Care (HUI2) could be improved. In absence of a formal measure, Shannon’s indices provide useful measures for assessing discriminatory power of utility instruments.
doi:10.1007/s11136-006-9160-6
PMCID: PMC1915610  PMID: 17294285
Health status; Methodology; Psychometrics; Population health; Health-related quality-of-life
18.  When outcome is a balance: methods to measure combined utility for the choice between induction of labour and expectant management in mild risk pregnancy at term 
Background
When the primary and secondary outcomes of clinical studies yield ambiguous or conflicting recommendations, preference or valuation studies may help to overcome the decision problem. The present preference study is attached to two clinical studies (DIGTAT, ISRCT10363217; HYPITAT, ISRCT08132825) that evaluate induction of labour versus expectant management in term pregnancies with a mild risk profile. The purpose of the present study is to compare four methods of valuation/preference measurement.
Methods
Multidimensional health state descriptions ('vignettes') defined by attributes and levels are presented to different response groups: laypersons, (ex-) patients, and medical experts. Valuations/preferences are measured with the Visual Analogue Scale (VAS), Time Trade-Off (TTO), Willingness to Pay (WTP) and Discrete Choice Experiment (DCE) techniques. These methods are compared in terms of feasibility, reliability and validity.
Anticipated results
By comparing the four techniques, we aim to answer (1) which of the techniques is most feasible, reliable and valid for use in multidimensional decision problems; (2) which of the techniques can be recommended for use in economic evaluations, and (3) do different response groups produce systematically different valuations, and if so, how can these be used to interpret preference results and to contribute to the development of clinical guidelines.
doi:10.1186/1471-2393-7-10
PMCID: PMC1949408  PMID: 17610715
19.  Individual differences in the use of the response scale determine valuations of hypothetical health states: an empirical study 
Background
The effects of socio-demographic characteristics of the respondent, including age, on valuation scores of hypothetical health states remain inconclusive. Therefore, we analyzed data from a study designed to discriminate between the effects of respondents' age and time preference on valuations of health states to gain insight in the contribution of individual response patterns to the variance in valuation scores.
Methods
A total of 212 respondents from three age groups valued the same six hypothetical health states using three different methods: a Visual Analogue Scale (VAS) and two variants of the Time trade-off (TTO). Analyses included a generalizability study, principal components analysis, and cluster analysis.
Results
Valuation scores differed significantly, but not systematically, between valuation methods. A total of 36.8% of variance was explained by health states, 1.6% by the elicitation method, and 0.2% by age group. Individual differences in the use of the response scales (e.g. a tendency to give either high or low TTO scores, or a high or low scoring tendency on the VAS) were the main source of remaining variance. These response patterns were not related to age or other identifiable respondent characteristics.
Conclusion
Individual response patterns in this study were more important determinants of TTO or VAS valuations of health states than age or other respondent characteristics measured. Further valuation research should focus on explaining individual response patterns as a possible key to understanding the determinants of health state valuations.
doi:10.1186/1472-6963-7-62
PMCID: PMC1868724  PMID: 17466068
20.  The natural course of spontaneous miscarriage: analysis of signs and symptoms in 188 expectantly managed women. 
BACKGROUND: Expectant management is an alternative for curettage in women with a miscarriage. AIM: To assess the pattern of vaginal bleeding and pain in expectantly managed women with a miscarriage, and to analyse the factors predictive of a relatively quick spontaneous loss of pregnancy. DESIGN OF STUDY: Part of a study comparing expectant management with surgical evacuation. SETTING: Two hospitals in Amsterdam. METHOD: In expectantly managed women with a miscarriage, the pattern of vaginal bleeding and pain and the probability of a spontaneous loss of pregnancy was analysed. RESULTS: Of the 188 expectantly managed women 95 (51%) experienced a spontaneous loss of their pregnancy. In women with bleeding at inclusion, 52% had a completed miscarriage loss, while of the women without bleeding but with a coincidentally diagnosed non-viable pregnancy during routine ultrasonographic examination, 46% had a completed miscarriage. In the multivariate analysis an increasing bleeding pattern at inclusion was predictive of a relatively quick spontaneous loss of pregnancy. The median daily levels of bleeding and pain were the most prominent during the first 8 days after the start of the bleeding and decreased thereafter. CONCLUSIONS: Expectant management is effective in 51% of unselected women with a miscarriage. An increasing bleeding pattern is predictive of a relatively quick spontaneous loss of pregnancy in first-trimester miscarriages. The graphical representation of our findings can be used to inform women about the natural course of miscarriages and a well-informed treatment choice.
PMCID: PMC1314693  PMID: 15103878
21.  Threatened miscarriage in general practice: diagnostic value of history taking and physical examination. 
BACKGROUND: Ultrasonography, the gold standard for establishing a diagnosis in first-trimester vaginal bleeding, is not always readily avaliable. Medical history and gynaecological examination are then used instead, to make a provisional diagnosis. AIM: To determine the diagnostic value of history taking and physical examination in first-trimester bleeding, to differentiate between patients requiring immediate further diagnostic examination from those in whom an expectant policy will initially suffice. DESIGN OF STUDY: Prospective population-based cohort study. SETTING: Seventy-four general practices in Amsterdam. METHOD: Two hundred and twenty-five patients with first trimester vaginal bleeding were referred for an early pregnancy assessment. The data from 204 patients were analysed. Two diagnostic models were constructed based on symptoms and the results of gynaecological examination to identify diagnostic subgroups relevant to clinical practice. RESULTS: Model 1, which separates viable pregnancies from other diagnoses, increased pre-test probability from 47% to a post-test probability of 70%. Model 2, which enabled the identification of complete miscarriages, resulted in a post-test probability of 41% of a complete miscarriage, given a pre-test sample probability of 25%. The tentative diagnosis of a general practitioner, based entirely on clinical judgement, turned out to be a poor predictor for the ultrasonographically confirmed diagnosis (pre-test probability of 47% changed to a post-test probability of 58%). CONCLUSION: This study shows that, in first trimester bleeding, neither statistical prediction models based on signs and symptoms, nor clinical judgement, are valid replacements for ultrasonographic assessment in establishing a diagnosis.
PMCID: PMC1316086  PMID: 12392123

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