USE OF CAPTURE-RECAPTURE TO ESTIMATE THE PREVALENCE OF OPIATE ADDICTION IN BARCELONA, SPAIN, 1989

It is difficult to obtain accurate prevalence estimates of opiate addi ction with direct methods. The capture-recapture method has been used to estimate the prevalence of hidden populations, including opiate add icts. In this study, we applied capture-recapture, including log-linea r modeling, to estimate the prevalence of opiate addicts in Barcelona, Spain. Anonymous identification data from three 1989 sources (hospita l emergency rooms, treatment admissions, and heroin overdose deaths) i n Barcelona were used to obtain population samples. For prevalence est imation, two strategies were followed: 1) emergency room data only, di vided into trimesters; and 2) all three sources used simultaneously. E stimates based only on emergency room data were lower than estimates o btained by the simultaneous analysis of all three data sources; the la tter estimates gave narrower confidence intervals (6,324-7,414 addicts ), giving a prevalence for Barcelona in 1989 of between 8.5 and 9.9 op iate addicts per 1,000 residents aged 15-44 years. The estimated preva lence varied by sex and age group and was highest in males aged 15-29 years (between 17.1 and 21.2). At least 42% had contacted one or more of the services studied, although only one in seven had been admitted for treatment during 1989. Capture-recapture is the election method fo r prevalence estimation when direct methods are not feasible.