RESUMEN
BACKGROUND: Many people with high-risk sexual or injection behaviors use harm reduction services with different identities and are therefore counted more than once in client databases. This practice results in inaccurate statistics on the number of clients served and the effective reach of these services. This study aimed to determine the levels of double counting of clients of harm reduction services, including needle and syringe programs, condom distribution, HIV testing and counseling, and methadone maintenance in five cities in Iran. METHODS: Between September and March 2020, our study included 1630 clients, 115 staff of harm reduction centers, and 30 experts in the field of harm reduction in five cities in Iran. Clients of harm reduction services were asked about using harm reduction services multiple times at the same center or at different centers in the last year using different identities. Estimates of double counting derived from client responses were validated by panels of center staff and experts in harm reduction. RESULTS: Synthesizing data from clients, staff, and experts, the final estimates of double counting of clients using harm reduction services were: HIV testing 10% (95% confidence interval [CI] 0-15), needle and syringe programs 17% (95% CI 8.5-20), condom distribution programs 13% (95% CI 3-19), HIV/STI counseling 10% (95% CI 0-16), and methadone maintenance 7% (95% CI 2-10). CONCLUSION: Double counting of clients in harm reduction services in Iran is substantial. Data on clients reach by harm reduction services need to be corrected for double counting to improve program planning, client population size estimation, and efficient resource allocation.