SENTINEL HOSPITAL SURVEILLANCE OF HIV-INFECTION IN QUEBEC

Objective: To measure the HIV seroprevalence rate in a surrogate sampl e of the general population in the province of Quebec, using a network of sentinel hospitals. Design: Anonymous unlinked sentinel surveillan ce study. Setting: Outpatient surgery units in 19 acute care hospitals throughout Quebec. Participants: All patients attending the outpatien t surgery units from November 1990 to October 1992. A total of 61 547 plasma samples were obtained from leftover blood samples collected for cell counts. Fifty samples were excluded because of an insufficient a mount of plasma and one because of an indeterminate result. Interventi on: HIV antibody testing with enzyme-linked immunosorbent assay; posit ive results confirmed with radioimmunoprecipitation assay. Outcome mea sures: HIV antibody status, sex, year of birth and area of residence. Results: The crude seroprevalence rate among the subjects aged 15 year s or more was 0.4 per 1000 population (95% confidence interval [CI] 0. 2 to 0.7) among the women and 3.6 per 1000 population (95% CI 2.8 to 4 .4) among the men (p < 0.001). The rate after adjustment for age, sex and geographic distribution of the study population was 2.3 per 1000 p opulation (95% CI 1.9 to 2.7). The seroprevalence rate among the male patients in the City of Montreal was much higher than the rates elsewh ere in the province. It increased progressively during each of the fou r 6-month intervals of the study: 8.1, 8.7, 13.9 and 18.3 per 1000 res pectively (chi(2) linear trend = 4.76; p = 0.029). No similar trends w ere observed outside Montreal for the male patients. There were too fe w seropositive female patients to draw any solid conclusion. Conclusio ns: Despite the possible drawbacks of a nonrandomized sampling scheme, this study suggests that in the male population the HIV seroprevalenc e rate is increasing in Montreal and is stable in all other areas of t he province. The continued surveillance of HIV infection through anony mous unlinked studies is useful to monitor trends.