Impact of monetary incentives on adherence to referral for screening chest X-rays after syringe exchange-based tuberculin skin testing

Introduction. Syringe-exchange programs (SEPs) have proven to be valuable sites to conduct tuberculin skin testing among active injection drug users. Chest x-rays (CXRs) are needed to exclude active tuberculosis prior to initiating treatment for latent tuberculosis infection. Adherence of drug users to referral for off-site chest x-rays has been incomplete. Previous cost modeling demonstrated that a monetary incentive to promote adherence could be justified on the cost basis if it had even a modest effect on adherence. Methods. We compared adherence to referral for chest x-rays among injection drug users undergoing syringe exchange-based tuberculosis screening in New York City before and after the implementation of monetary incentives. Results. From 1995 to 1998, there were 119 IDUs referred for CXRs based on tuberculin skin testing at the SEP. From 1999 to 2001, there were 58 IDUs referred for CXRs with a $25 incentive based on adherence. Adherence to CXR referral within 7 days was 46/58 (79%) among individuals who received the monetary incentive versus 17/119 (14%) prior to the implementation of the monetary incentive (P <.0001; odds ratio [OR] = 23; 95% confidence interval [CI] = 9.5-57). The median time to obtaining a CXR was significantly shorter among those given the incentive than among those referred without the incentive (2 vs. 11 days, P <.0001). In multivariate logistic regression analysis, use of the incentive was highly independently associated with increased adherence (OR = 22.9; 95% CI = 10-52). Conclusions. Monetary incentives are highly effective in increasing adherence to referral for screening CXRs to exclude active tuberculosis after syringe exchange-based tuberculin skin testing. Prior cost modeling demonstrated that monetary incentives could be justified on the cost basis if they had even a modest effect on adherence. The current data demonstrated that monetary incentives are highly effective at increasing adherence in this setting and therefore are justifiable on a cost basis. When health care interventions for drug users require referral off site, monetary incentives may be particularly valuable in promoting adherence.