PREDICTORS OF POSITIVITY FOR HEPATITIS-B AND THE DERIVATION OF A SELECTIVE SCREENING RULE IN A CANADIAN SEXUALLY-TRANSMITTED DISEASES CLINIC

Objectives: To determine the prevalence of hepatitis B surface antibod y (anti-HBs) and antigenemia (HBsAg), the risk factors for seropositiv ity and the effectiveness of a selective serologic screening rule amon g sexually transmitted diseases (STD) clinic attendees. Study design: Clients in the Hamilton STD Clinic were surveyed from October 1992 to July 1993 on sociodemographic, past medical, and behavioural data, wer e tested for several STDs and were offered serological testing and vac cination against hepatitis B. Predictors of seropositivity were determ ined by single variable analysis. A selective serologic screening rule was derived using logistic regression modelling. Results: The seropre valence of anti-HBs was 6.8% (21/310) in the 310 of 385 clients (80.5% ) who agreed to be tested and interviewed. There were no HBsAg carrier s. Five independent risk factors were identified by logistic regressio n: (1) age greater than 35 years; (2) birth outside Canada and histori es of; (3) syphilis; (4) gonorrhoea; or (5) injection drug use. If cli ents with at least one of these predictors had been tested, 34.5% woul d have been selected for serologic testing and 85.7% of all positives would have been detected. The screening rule was more effective for me n than for women. Conclusion: In this low prevalence setting, selectin g STD clinic clients based on the presence of any one of five risk pre dictors appears to be an effective strategy for hepatitis B serologic screening in the context of a Canadian vaccination program. (C) 1998 E lsevier Science B.V. All rights reserved.