Anal cytology as a predictor of anal intraepithelial neoplasia in HIV-positive men and women

Human immunodeficiency virus (HIV)-infected individuals have increased risk of anal intraepithelial neoplasia (AIN) and squamous cell carcinoma (SCC). Cytologic screening is invaluable in the detection of cervical neoplasia, therefore many clinicians have adopted anal cytology as part of anal cancer screening in patients at high-risk for anal neoplasia. The purpose of this study is to determine whether anal cytology is a valuable screening test for identifying AIN in HIV+ patients. The cohort included 228 HIV+ patients who underwent anal cancer screening with collection of 318 anal cytology specimens between January 2006 and December 2009. Of this group, 74 (32.5%) patients had associated anal biopsies within a 6-month period, with a total of 89 comparison cases. The anal cytology samples were classified using the 2001 Bethesda System terminology. The sensitivity of anal cytology in detecting ASC-US, AIN 1-3 or SCC was 93%. Cytology was 88% sensitive for detecting low-grade AIN (AIN 1), but only 20% sensitive for detecting high-grade AIN (AIN 2-3) or SCC. Atypical squamous cells of undetermined significance cases were distributed evenly between low- and high-grade AIN, with two cases having normal histology. Only six cases had negative cytology, all of which were associated with AIN on biopsy, for a false negative rate of 7%. Anal cytology is a good predictor of AIN, as confirmed by the high degree of sensitivity. However, there is poor correlation between the cytological and histological grade of AIN. Cytology underestimates the grade of dysplasia compared to the corresponding biopsy.