The prevalence, and predictive value, of abnormal anal cytology to diagnose anal dysplasia in a population of HIV-positive men who have sex with men.

Due to the increasing incidence of anal cancer in HIV-positive men who have sex with men, and the potential to detect and treat high-grade anal dysplasia--the putative anal cancer precursor--we have introduced an anal cytology screening service. Patients with abnormal anal cytology have follow-up high-resolution anoscopy (HRA) with biopsy of lesions clinically suspicious for high-grade dysplasia. In total, 244 men were screened and 235 (96%) of the samples were adequate for cytological interpretation using the Bethesda 2001 system. One hundred and sixty-four (67%) men had abnormal anal cytology, and 93 of them had follow-up HRA and anal biopsy. The positive predictive value for any anal cytological abnormality to predict any degree of anal dysplasia was 95.7+/-2.1%, and for any anal cytological abnormality to predict high-grade anal dysplasia was 55.9+/-5.1%. Abnormal anal cytology was highly predicative of anal dysplasia on biopsy.