The role of cytology (Pap tests) and human papillomavirus testing in anal cancer screening

OBJECTIVE: To assess anal oncogenic human papillomavirus (HPV) and anal cytology as screening tests for detecting high-grade anal intraepithelial neoplasia (AIN 2+), as this is an immediate anal cancer precursor. DESIGN: Cross-sectional study of 401 HIV-positive men who have sex with men (MSM). The endpoint was histologically confirmed AIN 2+ obtained by high-resolution anoscopy. Cytology and biopsy specimens were assigned random numbers and independently assessed by two pathologists. METHODS: We did concomitant anal cytology, anal HPV testing and HRA with directed biopsies without knowing the results of each intervention. The main outcome measures were the sensitivity, specificity, negative predictive value and positive predictive value of anal cytology and oncogenic HPV for the detection of AIN 2+. RESULTS: Cytology was abnormal in 67% of patients: high-grade squamous intraepithelial lesion, 12%; low-grade squamous intraepithelial lesion, 43% and atypical squamous cells of undetermined significance, 12%. Biopsies were abnormal in 68% of patients: AIN 2+, 25% and AIN 1, 43%. HPV was detected in 93% with multiple HPV types in 92% and oncogenic HPV types in 88%. Test performance characteristics for the detection of AIN 2+ using any abnormality on anal cytology were: sensitivity 84%, specificity 39%, negative predictive value 88% and positive predictive value 31%; using oncogenic HPV: sensitivity 100%, specificity 16%, negative predictive value 100% and positive predictive value 28%. CONCLUSION: Anal cytology and HPV detection have high sensitivity but low specificity for detecting AIN 2+. HIV-positive men who have sex with men have a high prevalence of AIN 2+ and require high-resolution anoscopy for optimal detection of high-grade anal dysplasia.