Factors associated with lack of awareness of HIV infection before diagnosis of AIDS.

OBJECTIVE: To identify characteristics of people likely to be unaware of their HIV infection before diagnosis of AIDS defining disease.
DESIGN: Survey of continuing surveillance of voluntarily reported AIDS cases.
SUBJECTS: 4127 adults with AIDS diagnosed during 1989-92 and reported to the Public Health Laboratory Service AIDS Centre.
SETTING: England and Wales. MAIN OUTCOME MEASURE: Lack of prolonged awareness of infection before diagnosis of AIDS, defined as an interval of nine months or less between first positive test result and diagnosis of AIDS.
RESULTS: Of 3556 adults with known dates of first positive HIV test result and AIDS diagnosis, 1742 (49%) had been unaware of their infection for up to nine months before AIDS was diagnosed. Lack of awareness was independently and positively associated with infection through heterosexual contact (odds ratio 4.46, 95% confidence interval 3.15 to 6.33), AIDS reported outside the Thames regions (1.64, 1.38 to 1.96), and being non-white (1.99, 1.51 to 2.61). Women were less likely to be unaware than men (0.50, 0.33 to 0.76), and people diagnosed in 1992 were least likely to be unaware (0.48, 0.39 to 0.60). Those aged 25-49 years at diagnosis were less likely to be unaware than those aged 15-24 years and those aged 50 and over.
CONCLUSIONS: People with certain characteristics are more likely than others to be unaware of their HIV infection before AIDS is diagnosed and are therefore less likely to receive prophylaxis. Methods for educating this heterogeneous group need to be investigated.