Screening and risk factors for anal cancer precursors in men infected with HIV in Taiwan

Homosexual men infected with human immunodeficiency virus (HIV) are at a greater risk of developing anal cancer. Men who are infected with HIV and visited the outpatient clinics in Taoyuan General Hospital were enrolled to this study. During March to December 2011, thin preparation anal Pap smear and human papillomavirus (HPV) genotyping were performed in 230 subjects, of which 69 subjects underwent anoscopic biopsy. Their mean age was 32.9±8.1 years, and 181 (78.6%) men were homosexual. The proportion and 95% confidence interval (CI) of subjects with anal dysplasia in cytology was 23.0% (17.56-28.44), including 13.4% (9.26-18.14) with atypical squamous cells of undetermined significance, 7.0% (3.70-10.30) with low-grade squamous intraepithelial lesions, and 2.6% (0.54-4.66) with high-grade squamous intraepithelial lesions. For participants having atypical squamous cells of undetermined significance or higher grades, multivariate logistic regression models yielded adjusted odds ratios (95% CI) of 12.61 (1.63-97.56) for homosexuality, 1.62 (1.31-2.00) for number of oncogenic HPV types, and 1.01 (1.00-1.02) for number of lifetime sexual partners. For detection of histological grade II or III anal intraepithelial neoplasm in anoscopic biopsies, the sensitivity of sequential tests for oncogenic HPV and cytology with atypical squamous cells of undetermined significance or higher grades was 100%. The positive likelihood ratio was 3.09 (P=0.05). It is important to consider anal cancer precursors among homosexual men who are infected with HIV. Anal cytology and oncogenic HPV genotyping testing are effective screening methods.