This novel method provides estimates of population size of hard-to-reach groups such as injecting drug users and men who have sex with men that are comparable with results derived by other methods. These estimates may be useful for the purposes of planning, implementing and evaluating prevention and care services, especially when they are combined with the results of other estimation methods to improve the degree of confidence in the resulting estimates.

The purpose of this study was to examine the HIV-testing behaviour of Canadians aged 15 years and older. Questions on HIV testing were asked as part of a Canada-wide random digit dialling telephone survey conducted in December 1995 to January 1996 on health practices and attitudes toward health care in Canada (n=3123). Including blood donation and insurance testing, 40.4% of men and 30.4% of women had been tested for HIV. Excluding blood donation and life-insurance testing (voluntary testing), 17.8% of men and 15.6% of women had been tested. In multivariate analyses, factors independently associated with voluntary testing among men were: having had sex with a man (OR=16.8), injection drug use (OR=5.8), having had a partner at high risk (OR=2.5), having received blood or clotting factor (OR=2.3), being younger than 45 years of age (OR=1.8), living in a city of over one million (OR=1.7), and making less than $30,000 a year (OR=1.6). For women, factors independently associated with voluntary testing were having received blood or clotting factor (OR=3.9), having had a high-risk partner (OR= 3.5), being younger than 45 years of age (OR=2.4), having had sex with a man (OR=2.3), and being unattached (OR=2.0). Results indicated that those at risk are more likely to be tested. It is of concern, however, that many of those reporting risk factors have not been tested. A better understanding of HIV testing behaviour is needed to improve the planning and evaluation of prevention and counselling services.