HIV-1 incidence determined retrospectively among drug users in Bangkok, Thailand.

OBJECTIVE: To measure trends in the incidence of HIV-1 infection among drug users in treatment at Thailand's largest drug detoxification unit. DESIGN: A retrospective cohort was established using computed, existing HIV-1 test results of 26,396 inpatients and outpatients admitted for 47,907 drug detoxification treatment courses from August 1987 to August 1992. METHODS: Matching of patient record numbers showed that 10,050 (38.1%) patients had been admitted two or more times during the period. From these, we selected a cohort of 7807 initially HIV-negative patients. Subsequent seroconversions among them were assumed to have occurred with uniform probability throughout the interval between the last HIV-negative and the first HIV-positive tests. RESULTS: There were 2311 (29.6%) seroconversions in the cohort. HIV-1 incidence among the 5974 (76.5%) who were injecting drug users (IDU) escalated from 20 new infections per 100 person-years (PY) of observation in 1987 to a peak of 57 per 100 PY in 1988, then gradually declining to a stable rate of about 11 per 100 PY during 1991 and 1992. Non-IDU (smokers, inhalers) constituted 683 (8.8%) of the cohort patients, and had HIV-1 incidence rates varying from 0.2 to five per 100 PY. 'Mixed' drug users, defined as individuals reporting different routes of drug administration on different admissions, composed 1150 (14.7%) of cohort patients and had an HIV-1 incidence rate between that of IDU and non-IDU. Prevalence of HIV-1 seropositivity among all IDU increased rapidly, from about 1% in early 1988 to a peak of about 40% by early 1989, and has remained stable through 1992. CONCLUSIONS: Prevention efforts must continue for IDU, since recent annual HIV-1 incidence remains high at > 10 per 100 PY. Such a high rate suggests that this group should be considered for HIV-1 vaccine efficacy trials. Stable HIV-1 prevalence can mask substantial incidence in a population with high turnover.

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 injection 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 capture listed all persons on methadone treatment for opiate addiction from April 17 through May 17, 1991, at 18 facilities in Bangkok. The second capture involved urine testing of persons held at 72 Bangkok police stations from June 3 through September 30, 1991. Persons whose urine tests were positive for opiate metabolites or methadone were included on the second list. RESULTS: The first capture comprised 4064 persons and the recapture 1540 persons. There were 171 persons included on both lists, yielding an estimate of 36,600 opiate users in Bangkok. Existing data indicate that 89% of opiate users in Bangkok inject drugs and that about one third are infected with HIV, yielding an estimate of approximately 12,000 HIV-infected injection drug users in Bangkok in 1991. CONCLUSIONS: During the 1990s the number of cases of acquired immunodeficiency 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 existing health care facilities. The capture-recapture method may be useful in estimating difficult-to-count populations, including injection drug users.

Evaluation of a 2-minute anti-human immunodeficiency virus (HIV) test using the autologous erythrocyte agglutination technique with populations differing in HIV prevalence.

A total of 1,800 blood specimens (1,000 from healthy blood donors, 300 from patients with sexually transmitted disease, and 500 from intravenous drug users) were simultaneously tested with anti-human immunodeficiency virus enzyme-linked immunosorbent assay (ELISA) kits and a newly developed 2-min test for anti-human immunodeficiency virus based on the principle of autologous erythrocyte agglutination (AGEN Biomedical Limited). We found that AGEN's rapid test was as sensitive and specific as the other ELISA kits.

High prevalence of delta virus infection in Thai intravenous drug abusers.

The prevalence of antibodies to delta virus (anti-delta) in the selected groups of hepatitis B surface antigenemia population was investigated. The subjects were 84 intravenous drug abusers; 20 chronic hepatitis, 12 cirrhosis, 6 primary hepatocellular carcinoma and 46 asymptomatic healthy carriers. Anti-delta was detected in 65.48% of intravenous drug abusers, 11.11% of chronic active hepatitis and 8.33% of cirrhosis cases. None of asymptomatic carriers had anti-delta. In addition, 51 acute icteric hepatitis B patients who were positive for HBs Ag and 20 IV drug abusers positive for anti-HBc only (HBsAg and anti-HBs negative) were negative for anti-delta.