The Role of Cytology (Pap Tests) and Human Papillomavirus Testing in Anal Cancer Screening

In the current study, investigators assessed anal oncogenic human papillomavirus (HPV) and anal cytology as screening tests for detecting high-grade intraepithelial neoplasia (AIN 2+), since this is an immediate precursor to anal cancer.

A cross-sectional study of 401 HIV-positive men who have sex with men was performed, with the endpoint being histologically confirmed AIN 2+ obtained by high-resolution anoscopy (HRA). Two pathologists assigned random numbers and independently assessed the cytology and biopsy specimens.

Concomitant anal cytology, anal HPV testing, and HRA with directed biopsies were conducted without knowledge of 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 AIN 2+ detection.

Sixty-seven percent of patients had abnormal cytology: high-grade squamous intraepithelial lesion, 12 percent; low-grade squamous intraepithelial lesion, 43 percent; and atypical squamous cells of undetermined significance, 12 percent. Abnormal biopsies were found in 68 percent of patients: AIN 2+, 25 percent and AIN 1, 43 percent. HPV was detected in 93 percent, with multiple HPV types found in 92 percent and oncogenic HPV types in 88 percent. "Test performance characteristics for the detection of AIN 2+ using any abnormality on anal cytology were: sensitivity 84 percent, specificity 39 percent, negative predictive value 88 percent, and positive predictive value 31 percent; using oncogenic HPV: sensitivity 100 percent, specificity 16 percent, negative predictive value 100 percent, and positive predictive value 28 percent."

"Anal cytology and HPV detection have high sensitivity but low specificity for detecting AIN 2+," the investigators concluded. "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."

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