ESTIMATING THE NUMBER OF HIV-INFECTED INJECTION-DRUG USERS IN BANGKOK- A CAPTURE-RECAPTURE METHOD

Objectives. The purpose of the study was to estimate the number of inj ection drug users infected with the human immunodeficiency virus (HIV) in Bangkok to allow planning for health services for this population. Methods. A two-sample capture-recapture method was used. The first ca pture listed all persons on methadone treatment for opiate addiction f rom April 17 through May 17, 1991, at 18 facilities in Bangkok. The se cond capture involved urine testing of persons held at 72 Bangkok poli ce stations from June 3 through September 30, 1991. Persons whose urin e tests were positive for opiate metabolites or methadone were include d on the second list. Results. The first capture comprised 4064 person s and the recapture 1540 persons. There were 171 persons included on b oth lists, yielding an estimate of 36600 opiate users in Bangkok. Exis ting data indicate that 89% of opiate users in Bangkok inject drugs an d that about one third are infected with HIV, yielding an estimate of approximately 12000 HIV-infected injection drug users in Bangkok in 19 91. Conclusions: During the 1990s the number of cases of acquired immu nodeficiency syndrome (AIDS) and other HIV-related diseases, including tuberculosis. in the population: of HIV-infected injection drug users in Bangkok will increase dramatically, placing new demands on existin g health care facilities. The capture-recapture method mag; be useful in estimating difficult-to-count populations, including injection drug users.