Anal cytology and p16 immunostaining for screening anal intraepithelial neoplasia in HIV-positive and HIV-negative men who have sex with men: a cross-sectional study

Akin to cervical cancer in sexually-active women, men who have sex with men (MSM) are predisposed to anal cancers, especially those with HIV co-infection. This cross-sectional study endeavored to assess the prevalence of anal dysplasia using Pap smears and p16 immunostaining amongst Indian MSM. A total of 31 consecutive HIV-positive and 34 HIV-negative MSM, from a cohort of sexually transmitted infection clinic attendees, underwent anal cytological evaluation with Pap smear and p16 staining. Chi square test and coefficient of correlation were used for comparison. Eighteen (27.7%) had abnormal anal cytology; increased in HIV-positive as compared to HIV-negative men (35% versus 20%, p=0.180). Similarly, both low-grade (25.8% versus 17.6%) and high-grade lesions (8.3% versus 4.8%) were comparable in HIV-positive and HIV-negative group. Thirteen (20%) smears were p16-positive with a sensitivity and specificity for anal dysplasia of 72.3% and 100%, respectively. Anal cytology may be used to screen for anal dysplasia in MSM irrespective of HIV status. Furthermore, the addition of p16, with greater specificity for high-grade lesions, may improve diagnostic accuracy especially for high-grade lesions. A larger study to further corroborate these observations is warranted.