P E Hasvold and R Wootton Telephone and SMS reminders Figure 1 The PRISMA ﬂowchart for the paper selection process while the mean cost of SMS or automated phone call reminders was E 0.14. The three highest reported costs were from phone reminders. While savings were estimated in 10 papers, the circumstances and cases could not be compared. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The present study concerns a systematic review of the use of telephone reminders (manual and automated) to improve attendance at hospital appointments. All studies except one found that sending reminders improved DNA rates. This suggests the possibility of publication bias, although we found no evidence that this was the case. Taking into account the quality of the studies, the pooled estimates show that manual reminders can achieve a reduction in the DNA rate of 39% of the baseline value, while automated reminders can achieve a reduction of 29% of the baseline value. It seems intuitive that reminders from a health-care professional would be more effective than those sent automatically by a computer. Our pooled estimate of effect size was based on a weighted mean, using study quality as the weighting factor. We did not attempt a formal meta-analysis for several reasons. First, only nine of the 29 studies were RCTs. Second, the studies were very heterogeneous. Finally, it was not possible to estimate the SE of the treatment effect from many of the published reports. Most of the papers reported the absolute change in DNA. We used the relative change in DNA to Table 2 Study characteristics Study size Duration of intervention (months) Reminder time (days before appointment) Baseline DNA rate (%) Intervention DNA rate (%) Absolute change in DNA rate (%) Relative change (% of baseline value) Table 3 DNA rates reported in 29 studies (33 estimates), unweighted Lower Median quartile 823 3 2.75 325 2 1.00 Upper quartile 2864 7 3.13 Median 23.1 12.5 7.0 38.1 Lower quartile 15.4 8.1 4.2 24.1 Upper quartile 27.0 19.4 11.5 58.0 Figure 2 Study quality (median quality score ¼ 7) Journal of Telemedicine and Telecare Volume 17 Number 7 2011 361