Comparison of 2 anal cytology protocols to predict high-grade anal intraepithelial neoplasia.

OBJECTIVES

Nylon-flocked and Dacron swab anal cytology collection procedures were evaluated for detecting high-grade anal intraepithelial neoplasia.

MATERIALS AND METHODS

Cross-sectional data for 42 HIV-infected and 16 uninfected men who have sex with men have been used. Sequentially collected anal cytology specimens, high-resolution anoscopy, and medical biopsy evaluated the sensitivity and specificity of cytology for predicting high-grade anal intraepithelial neoplasia. Men showing atypical squamous cells (ASC) or more severe findings by cytology were compared with those showing negative for intraepithelial lesions.

RESULTS

The prevalence of high-grade anal intraepithelial neoplasia was 35% (21/58), and findings were approximately 1.5 times higher among HIV-infected compared with uninfected men. Unsatisfactory cytology was twice as common among Dacron compared with nylon-flocked swab protocol specimens (14% [8/58] vs 7% [4/58]). Sensitivity and specificity for the nylon-flocked protocol cytology showing ASC or more severe findings were 81% (58%-95%) and 73% (50%-89%), respectively. Dacron protocol specimens showed 52% (30%-74%) and 58% (34%-80%) sensitivity and specificity, respectively. Men showing ASC or more severe findings using the nylon-flocked protocol cytology showed 3-fold higher odds for high-grade anal intraepithelial neoplasia compared with men with negative results (p < .05), but no statistically significantly higher odds of high-grade anal intraepithelial neoplasia for men showing ASC or more severe findings compared with those with negative results for Dacron protocol cytology (p > .05).

CONCLUSIONS

The nylon-flocked protocol better detects high-grade anal intraepithelial neoplasia than does the Dacron protocol, yields more interpretable results, and classifies men with high-grade anal intraepithelial neoplasia as cytologically abnormal 2.5 times more often, even in this small clinical trial.

CLINICAL TRIALS REGISTRATION NUMBER

NCT00955591.