Patients who had received an SMS reminder were significantly more likely to attend their ophthalmology hospital appointments compared to those who had not received an SMS. This study showed that sending SMS reminders led to a 6.9% absolute reduction and 38% relative reduction in non-attendance rates for ophthalmology outpatient appointments. Non-attendance rates in the SMS group and the control group were 11.2% and 18.1%, respectively. The cancellation of appointments in the SMS group compared to the control group was slightly higher (13.4% vs 11.2%). Cancellation rates were not statistically significantly different between the two groups but there was a trend towards a higher cancellation rate in the SMS group (relative risk of cancellation 1.26; 95% CI 0.98–1.61).
The non-attendance rate for ophthalmology appointments (18.1%) in our control group was higher than the mean non-attendance rate for all the different hospital specialty outpatient appointments (12.1%). This confirmed that non-attendance was a greater problem for the ophthalmology department compared to many other specialties within the same hospital. It is difficult to speculate why this might be, but there could have been administration problems, for example, due to staff shortages; or perhaps, though this may be unlikely, the demographic characteristics or behaviours of the patients in this geographical area who attend the ophthalmology clinics may differ from that of other specialties. The 18.1% non-attendance rate in the control group in our study is higher than that quoted in other studies [19
]. For example, the Birmingham ophthalmology department audit, over a year, was 12.6% [18
]. However, our study was only conducted over a 6 month period and ideally, information relating to a year, taking into account seasonal variations, would be valuable. Also, this Birmingham study was in 1990–1, so non-attendance rates may have changed over this time period. A New Zealand audit showed a non-attendance rate of 17.2% [17
The non-attendance rate of the SMS group in our study was 38% lower than that of the control group (RR = 0.62) and there was strong evidence (P = 0.0002) to reject the null hypothesis of no difference between these two groups. A multi-centred, randomised controlled trial in China also found an increase in the likelihood of attendance (OR = 1.59, P = 0.005) [20
]. This study had 993 participants who were divided into 3 study arms; and compared SMS reminders and mobile telephone conversations reminders with a control group of no intervention. There was no statistically significant difference in non-attendance observed between their SMS group and mobile phone-call reminders. This study was conducted in a primary care setting, which may have represented a systematically different group of patients in terms of non-attendance characteristics to those attending secondary care appointments, so direct comparisons cannot be made. Additionally, Family Practice-based factors such as mistakes or misunderstandings surrounding appointment details, relayed over the telephone, from the health provider are possible reasons for non-attendance in this healthcare setting [21
The percentage reduction in non-attendance rates with SMS reminders of 6.9% in our study is lower than that reported for a recent study in an Irish ENT outpatient department [2
], where there was a 11.6% reduction (from 33.6% to 22%). This study, however, used data from a much larger sample size (3981 patients) and covered a 3 year period. Studies of other methods of appointment reminders such as posted letters and telephone calls found reductions of non-attendance rates between 6% and 19% [6
]. The reduction in non-attendance found in our study is within the range of these other studies. Therefore, SMS reminders are at least as effective as alternative methods. The SMS reminders also have the advantage of being more cost-effective and requiring less labour than the other methods.
Limitations of this study
Although there seems to be an association between the use of SMS reminders and a decrease in non-attendance rates, this is not necessarily causal and there could be confounding factors and biases which may partially or fully explain this association. This study suggests that the use of SMS reminders could help to reduce ophthalmology non-attendance rates. However, the design in this paper is sub-optimal, and a rigorous randomised controlled trial, stratified by socio-demographic characteristics and clinical conditions, is required to determine if the potential benefits observed in this study can be replicated. Knowledge of the patients' clinical presentation in the intervention and control groups is also important as it could affect the 'value' placed on it by patients and potentially affect the likelihood of an appointment being kept.
We do not know what proportion of the control group owned mobile phones, but whose mobile number was not available for this service. We are also unaware of the number of patients who were unfamiliar with using text-messaging and so unable to read the reminder. There could also have been participation bias, as the SMS group patients (who provided a mobile phone number) may have been a more motivated group of patients; and these patients may have been more likely to attend their appointments irrespective of receiving an SMS reminder. This could have potentially led to an over-estimate of the association between SMS reminders and non-attendance rates. Data was only available for a 6 month period, and so did not take account of seasonal and monthly variations in non-attendance. However, using the same time-frame for the controls helped to reduce the chance of monthly and seasonal variations contributing to the observed differences. We did not have demographic information relating to those patients who owned a mobile phone or for those who received an SMS reminder who subsequently attended and did not attend their scheduled appointments. Data relating to potential confounding factors (such as age, sex, ethnicity and socio-economic status) was not collected, so we were not able to adjust for these in the statistical analysis. We did not have demographic information available relating to age in either groups and recognise this is a weakness and could account, in part or fully, for the observed difference. However, as younger patients are more likely to own mobile phones and also have higher non-attendance rates, the fact that the non-attendance rate decreased in the SMS group (who are more likely to be younger), suggests that use of SMS reminders may be beneficial to target younger patients. Finally, patients who received SMS reminders were for a first consultation and it has been suggested that follow-up appointments have higher non-attendance rates [22
]. This was the first stage of the study; the next stage will be focusing on follow-up appointments.
What this study adds
SMS appointment reminders seem to be an effective and efficient method of improving ophthalmology outpatient attendance, which is less labour intensive than the more traditional reminder systems that have been used in the past. The facility for patients to reply or call in response to an SMS reminder to cancel their appointment can help to reduce the non-attendance rates and free up appointments for other patients, which otherwise may be lost. We cannot extrapolate our findings to other specialties or hospitals; so future research should include suitably powered randomised controlled trials for assessing SMS appointment reminders for ophthalmology and other specialties to assess the cost-effectiveness within the NHS. The use of SMS technology is expanding and has already been used to help in the management of some health problems and diseases; for example, asthma [23
] and diabetes [24
] management and smoking cessation [26
]. Hence, the potential scope for the further utilisation of this technology is tremendous. SMS reminders could offer a cost-effective method for reducing non-attendance rates for retinal screening appointment follow-ups for diabetic patients.
Strengths and weaknesses of SMS technology
In addition to the advantages already described, SMS reminders require minimal investment in IT infrastructure, as this is already in existence; as the IT software for sending automated SMS integrates with existing electronic patient health records and hospital administrative database systems. Once the system is in place, the cost of running the service increases very little as the number of SMS reminders increases. As they are automated messages, it does not require staff training so this offers a time, labour and cost-efficient system.
There are a number of potential weaknesses. Patients may not receive the SMS reminders due to incorrect data entry. However, this problem can occur with other methods of appointment reminders such as letters and telephone calls (with change of address) [12
]. The uses of different technologies are very fluid and dynamic and so it is not known how the use of mobile phones and the use of SMS technology will evolve over time. However, it is anticipated that there will be an increase in mobile phone ownership and use of SMS messaging facilities in the immediate few years. Elderly people have lower ownership rates of mobile phones and may not be able to use SMS facilities [27
]. The Office for National Statistics (UK) [27
] found mobile ownership in 2003 varied by age, with nearly 90% of 15–24 year olds owning one and less than a quarter of those aged 75 years and over owning one in 2003. However, between 2001 and 2003, the largest increases in ownership were amongst those aged 75 and over, with the proportions almost doubling [27
]. However, it has traditionally been younger patients who have missed their outpatient appointments more than older patients, so the use of SMS reminders could be targeted towards patients under 60 years old.
There is always some wastage in any system and the real cost of a missed appointment is difficult to quantify. It may be, in some cases, that the appointment may not have really been needed, although this is difficult to prove. For example, patients' agenda may influence presentation and attendance [28
]. Based on the 'number needed to text' analysis, approximately fourteen people would need to be sent an SMS reminder to prevent one non-attendance. As the cost of outpatient appointments is considerable, this could potentially be worthwhile, but needs to be tested through a more rigorous economic analysis. A well-designed randomised controlled trial would give a more accurate representation of the NNT to prevent one non-attendance. Only around 5% of the patients with scheduled ophthalmology appointments were sent SMS reminders in this study; so, if the reminders were sent on a much larger scale to patients with first and follow-up appointments and for all the departments in the hospital, the savings to the NHS could be large. A previous cost-effectiveness analysis has estimated that the annual direct cost of missed hospital appointments in England is estimated to be close to £575 million [1
] and that the use of SMS-based reminders could lead to a potential saving of £55.6 to £83.5 million a year [1
], so the potential scope for this technology is considerable.