Figure 5 Absolute change in DNA for manual and automated (SMS or automated phone call) reminders P E Hasvold and R Wootton Telephone and SMS reminders Figure 3 Funnel plot of relative change in DNA rate (% of baseline value) compensate for the different baseline DNA rates in the different settings of the studies. Although the quality of the economic data was weak, the apparent cost of sending reminders was much lower than the expected savings from avoided missed appointments. The time between the reminder and the appointment did not seem to have any strong effect on the DNA rate for any of the methods (see Figure 4). All studies involved reminders being sent out within a week, which appears to be an appropriate time ahead of an appointment to avoid people forgetting about it. An analysis of the relation between the age of the patients and the observed effect showed no difference between the age groups. Limitations In the papers which studied two kinds of reminder simultaneously, we treated the two arms as independent Figure 4 Effect size (relative change in DNA rate) and the time at which the reminder was issued 362 Journal of Telemedicine and Telecare Volume 17 Number 7 2011 Figure 6 Relative change in DNA (% of baseline) for manual and automated (SMS or automated phone call) reminders studies since they were separate groups, when there might have been interdependencies. Our initial search was conducted using a single database and clearly if more databases had been used, more references might have been found. However a study by Bahaadinbeigy et al.35 suggests that more than 80% of telemedicine papers can be found by searching in Medline alone. We also conducted a search in the Psycinfo database, Table 4 Pooled estimates Manual reminders absolute change in DNA 18 rate (%) relative change in DNA rate 18 (% baseline) Automated reminders absolute change in DNA 15 rate (%) relative change in DNA rate 15 (% baseline) No of estimates Weighted mean Unweighted mean 8.3 39.1 8.9 28.9 8.9 42.2 9.7 32.5