Twenty years of telemedicine in chronic disease management--an evidence synthesis.

A literature review was conducted to obtain a high-level view of the value of telemedicine in the management of five common chronic diseases (asthma, COPD, diabetes, heart failure, hypertension). A total of 141 randomised controlled trials (RCTs) was identified, in which 148 telemedicine interventions of various kinds had been tested in a total of 37,695 patients. The value of each intervention was categorised in terms of the outcomes specified by the investigators in that trial, i.e. no attempt was made to extract a common outcome from all studies, as would be required for a conventional meta-analysis. Summarizing the value of these interventions shows, first, that most studies have reported positive effects (n = 108), and almost none have reported negative effects (n = 2). This suggests publication bias. Second, there were no significant differences between the chronic diseases, i.e. telemedicine seems equally effective (or ineffective) in the diseases studied. Third, most studies have been relatively short-term (median duration 6 months). It seems unlikely that in a chronic disease, any intervention can have much effect unless applied for a long period. Finally, there have been very few studies of cost-effectiveness. Thus the evidence base for the value of telemedicine in managing chronic diseases is on the whole weak and contradictory.