Background Patient adherence to medications, particularly for conditions requiring prolonged treatment such as tuberculosis, is frequently less than ideal, and can result in poor treatment outcomes. Material incentives (given as cash, vouchers and tokens), have been used to improve adherence. Objectives To assess the effects of material incentives in people undergoing diagnostic testing, or receiving prophylactic or curative therapy, for tuberculosis. Search methods We undertook a comprehensive search of the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; EMBASE; LILACS; Science Citation Index; and reference lists of relevant publications; to 22 June 2011. Selection criteria Randomized controlled trials of material incentives in patients being investigated for tuberculosis, or on treatment for latent or active disease. Data collection and analysis At least two authors independently screened and selected studies, extracted data, and assessed the risk of bias. The effects of interventions are compared using risk ratios (RR), and presented with 95% confidence intervals (CI). The quality of the evidence was assessed using GRADE. Main results We identified 11 eligible studies. Ten were conducted in the USA: in adolescents (one trial), in injection drug or cocaine users (four trials), in homeless adults (three trials), and in prisoners (two trials). One additional trial recruited malnourished men receiving active treatment for tuberculosis in Timor-Leste. Material incentives may increase the return rate for reading of tuberculin skin test results compared to normal care (two trials, 1371 participants: RR 2.16, 95% CI 1.41 to 3.29, low quality evidence). Similarly, incentives probably improve clinic re-attendance for initiation or continuation of antituberculosis prophylaxis (three trials, 595 participants: RR 1.58, 95% CI 1.27 to 1.96, moderate quality evidence), and may improve subsequent completion of prophylaxis in some settings (three trials, 869 participants: RR 1.79, 95% CI 0.70 to 4.58, low quality evidence). We currently don't know if incentives can improve long-term adherence and completion of antituberculosis treatment for active disease. Only one trial has assessed this and the incentive, given as a daily hot meal, was not well received by the population due to the inconvenience of attending the clinic at midday (one trial, 265 participants, RR 0.98, 95% CI 0.86 to 1.12, very low quality evidence). Several trials have compared different forms or levels of incentive. These comparisons remain limited to single trials and robust conclusions cannot be made. In summary, cash incentives may be more effective than non-cash incentives (return for test results: one trial, 651 participants: RR 1.13, 95% CI 1.07 to 1.19, low quality evidence, adherence to tuberculosis prophylaxis: one trial, 141 participants: RR 1.26, 95% CI 1.02 to 1.56, low quality evidence) and higher amounts of cash may be more effective than lower amounts (return for test results: one trial, 404 participants: RR 1.08, 95% CI 1.01 to 1.16, low quality evidence). Material incentives may also be more effective than motivational education at improving return for tuberculin skin test results (low quality evidence), but may be no more effective than peer counselling, or structured education at improving continuation or completion of prophylaxis (low quality evidence). Authors' conclusions There is limited evidence to support the use of material incentives to improve return rates for tuberculosis diagnostic test results and adherence to antituberculosis preventive therapy. The data are currently limited to trials among predominantly male drug users, homeless, and prisoner subpopulations in the USA, and therefore the results are not easily generalised to the wider adult population, or to low-and middle-income countries, where the tuberculosis burden is highest. Further high-quality studies are needed to assess both the costs and effectiveness of incentives to improve adherence to long-term treatment of tuberculosis.
