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 th e Bronx, New York. OBJECTIVE: To define whether costs associated with directly observed preventive therapy (DOPT) of tuberculosis are justif ied 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 t uberculosis infection and disease, and costs of screening, chemoprophy laxis, direct observation and treatment of active disease. The cost-ef fectiveness of providing DOPT to this population was modeled. RESULTS: We assessed the impact of providing DOPT to 151 eligible persons. Ass uming 65% isoniazid effectiveness, and incorporating costs of screenin g, observed chemoprophylaxis and clinical monitoring, a net savings in tuberculosis-related hospital costs of $285 284 ($563 per person scre ened) was associated with DOPT ($10 274 per case prevented). Direct ob servation 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-s ensitive disease across a range of parameter values. CONCLUSIONS: Prov iding DOPT is a highly cost-effective intervention for drug users in t reatment. Commitment of additional resources required for DOPT should be given priority in this and other populations at high risk for tuber culosis.