Factors associated with clinical and sub-clinical anal human papillomavirus infection in homosexual men

Abstract

Objectives: (I) to determine the relative sensitivities of clinical examination, cytology and HPV DNA hybridisation for the detection of anal human papillomavirus infection; and (ii) to examine various factors which may influence presentation of anal human papillomavirus infection in homosexual men.

Methods and results: 112 unselected homosexual men attending a Sydney STD clinic for routine screening underwent a complete anogenital and physical examination, during which blood samples (for haematological, serological and immunological investigations), rectal swabs (for culture of anal pathogens) and anal scrapes of the dentate line (for cytology and HPV DNA hybridisation) were collected. Papanicolaou-stained anal smears were examined for cytological abnormalities, including those indicative of HPV infection or anal intraepithelial neoplasia (AIN). HPV DNA was detected by high stringency dot hybridisations using radiolabelled HPV 6, 11, 16 and 18 DNA probes. Visible anal condylomata, situated either externally or in the anal canal, were present in 26% of these men; 46% had cytological evidence of HPV infection, and 19% of the smears showed evidence of mild to moderate dysplastic changes (AIN I-II). Detectable HPV DNA was present in 40% of the anal scrapes. By combining these results, a total of 73 men (65%) were found to have at least one of the indicators of HPV infection. These data, together with that relating to HIV antibody, immune status and past or present infection with other STDs, was correlated with information obtained from a questionnaire administered to the patients at the time of their clinical examination.

Conclusions: In this study cytology was found to be slightly more sensitive than HPV DNA dot hybridisation for the detection of HPV infection in the anal canal, providing the full range of HPV-associated cytological changes were accepted as a basis for diagnosis. Clinical anal lesions were more likely to be detected in young men, men who had symptomatic HIV infection and those with a history of past anal wart infection. The latter group also had a higher incidence of cytologically apparent HPV infection in their anal smears. There was a significant association between the detection of HPV 16/18 and the presence of anal dysplasia, but there were no significant correlations between HPV infection or anal dysplasia and HIV antibody, immune function status, sexual practices or history of other STDs.