Screening for anal high-grade squamous intraepithelial lesions with flexible endoscopy in high-risk individuals

Anal squamous cell carcinoma is increasingly prevalent among men who have sex with men (MSM) living with HIV, related to anal dysplasia associated with persistent Human Papillomavirus (HPV) infection. While high-resolution-anoscopy (HRA), using colposcopy and a rigid anoscope, is the diagnostic standard, it is resource-intensive and not widely available. This study evaluates flexible endoscopy compared to cytology and anal HPV for detecting high-grade squamous intraepithelial lesions (HSIL) in a structured screening protocol.

HIV-positive MSM (n = 304) were consecutively recruited during routine HIV monitoring. Anal samples were collected for cytology and HPV testing. Participants underwent high-resolution flexible endoscopy of the anal canal (HR-FEA), with endoscopic resection of suspected lesions and histopathological follow-up.

Of 304 participants, 286 underwent HR-FEA where lesions were found in 80%. After 12 additional dropouts, 218/274 underwent resections. HSIL was found in 67/274 (24%) and LSIL in 61/274 (22%). Resected lesions were dysplastic in 59%. HPV testing showed 64% sensitivity and 72% specificity for HSIL; cytology had 15% sensitivity and 96% specificity. Combined testing (cytology/HPV) improved overall dysplasia detection but not HSIL beyond HPV alone. Both methods missed many HSILs found by endoscopy. Tolerability was high; 99% would repeat.

This study assessed HR-FEA for HSIL screening in MSM living with HIV, comparing its diagnostic performance to anal cytology and HPV, and evaluating acceptability. HPV showed higher sensitivity, cytology higher specificity, while both tests missed many lesions compared to HR-FEA. Although specificity in HR-FEA was related to frequently occurring non-dysplastic lesions, HR-FEA was effective and well-tolerated.