Our results indicate that, despite a significant increase in new studies, no robust effect of TM on HbA1c was observed at the end of the intervention. It remains possible that TM has a small effect on HbA1c, but our data argue against a large effect. Our pooled analysis includes more than 100 subjects per group giving us enough power to detect a difference in HbA1c of 0.5%. Therefore, if there is an effect of the intervention on HbA1c, it is likely less than 0.5%. Our results are consistent with a recent randomized control trial examining the effect of telemedicine case management for diabetes in an older population. This study involving 1,665 subjects found an estimated 0.29% difference in HbA1c favoring telemedicine at the end of 5 years between groups [20
We do not believe that lack of effect stems from selection bias among included studies. We did not expand our definition to include all uses of telemedicine, including web-based education modules and teleconferences to conduct remote clinic visits that did not necessarily include routine transmission of and feedback on blood glucose results, because that would have resulted in a collection of heterogeneous interventions among which a combination and comparison of outcomes would have been inappropriate in a meta-analysis. Moreover, upon reviewing studies that were excluded by our methods, we found that the results of those studies excluded were similar to those that were included. Three randomized controlled trials that were excluded from our review, because they did not involve transmission of blood glucose data, also found no effect on glycemic control [21
Episodes of severe hypoglycemia and DKA were rare and did not differ between groups. Although data were limited, there were no apparent differences in QoL or patient satisfaction between groups. One study that used TM to replace a clinic visit suggests a reduction in cost with no increase in adverse effects. Although we might have expected adolescents to be more engaged in a telemedicine intervention compared to younger children, a between-study comparison found no differences in pooled estimates of HbA1c at the end of the intervention between subgroups based on age. However, it is possible that future, more technology-based interventions may fare better.
We used the GRADE system because it provides explicit and comprehensive criteria for assessing the quality of a body of evidence. We recognize that based on this system, the evidence in our study was determined to be low. This was, in part, due to a necessary downgrade for the use of HbA1c as an indirect measure. However, based on the results of the DCCT [1
], HbA1c is regarded as a reliable surrogate marker for long-term complications in T1DM. Therefore, the quality of evidence is likely better than is reflected by the GRADE system.
Despite disappointing initial results, many aspects of TM interventions warrant further study. For example, between-study subgroup analyses suggest a trend toward a greater effect of TM on HbA1c among participants with the highest baseline HbA1c. Thus, determining whether TM could be an important adjunct for patients with the poorest glycemic control is worth further investigation in well designed, adequately powered, long-term studies.
Although our study found no overall effect on glycemic control, it did not identify any detrimental effects. Thus, other factors to consider include whether TM may be more effective in subgroups of youth such as those living remotely from the centres where care is provided. Reducing the number of clinic visits, while maintaining glycemic control, would be clinically desirable and potentially cost-effective. Thus, more studies are also needed to examine the cost-utility of TM and to determine the effects of TM interventions that replace aspects of diabetes care. Such studies should consider if TM would result in missed opportunities for screening for complications and/or education.
Finally, it will also be important to determine whether the effect of TM differs depending on the expertise of the individuals administering the TM, the frequency, and mode of data transmission (SMS, email, mobile phone, smart phone, personal digital assistant (PDA)) and whether the intervention involves the youth and/or their caregivers, or the setting. One study that examined TM in the school setting found that there was a decrease in the number of urgent visits to school nurses and calls to the diabetes centers. Successful implementation of a school-based TM intervention depends on the particular structure of the school system and may not be feasible where there are no school nurses.
It was surprising that more of the recent studies did not use more novel modes of data transmission such as SMS or other telephone-based strategies. It is possible that future studies examining the effects of newer technologies may show different results compared to the studies currently available for review. In addition to glycemic control and complications, such studies should measure other patient-important outcomes such as QoL, diabetes knowledge, and patient satisfaction.