Cost-effectiveness of directly observed chemoprophylaxis of tuberculosis among drug users at high risk for tuberculosis

SETTING: A methadone treatment program with on-site medical care in the Bronx, New York. OBJECTIVE: To define whether costs associated with directly observed preventive therapy (DOPT) of tuberculosis are justified by cases and costs of tuberculosis prevented among persons at high risk for active disease. DESIGN: Detailed data were collected on drug users in treatment regarding human immunodeficiency virus (HIV) and tuberculosis infection and disease, and costs of screening, chemoprophylaxis, direct observation and treatment of active disease. The cost-effectiveness of providing DOPT to this population was modeled. RESULTS: We assessed the impact of providing DOPT to 151 eligible persons. Assuming 65% isoniazid effectiveness, and incorporating costs of screening, observed chemoprophylaxis and clinical monitoring, a net savings in tuberculosis-related hospital costs of $285 284 ($563 per person screened) was associated with DOFF ($10274 per case prevented). Direct observation of chemoprophylaxis proved cost-effective if associated with even a 10% increment in overall isoniazid effectiveness compared with self- administered chemoprophylaxis. DOPT costs per tuberculosis case averted remained below the in-patient costs of a single case of drug-sensitive disease across a range of parameter values. CONCLUSIONS: Providing DOPT is a highly cost-effective intervention for drug users in treatment. Commitment of additional resources required for DOPT should be given priority in this and other populations at high risk for tuberculosis.