A composite cytology-histology endpoint allows a more accurate estimate of anal high-grade squamous intraepithelial lesion prevalence

Background: There is debate about the accuracy of anal cytology and high-resolution anoscopy (HRA), in the diagnosis of anal human papillomavirus (HPV)-related squamous intraepithelial lesions (SIL). Few studies have performed both simultaneously in a large sample of high-risk individuals. Methods: At baseline in a community-based cohort of HIV-infected and uninfected homosexual men ages ≥35 years in Sydney, Australia, all men underwent anal swabbing for cytology and HPV genotyping, and HRA-guided biopsy. We evaluated the separate and combined diagnostic accuracy of cytology and histology, based on a comparison with the prevalence of HPV16 and other high-risk (HR) HPV. We examined trends in HPV prevalence across cytology-histology combinations. Results: Anal swab, HRA, and HPV genotyping results were available for 605 of 617 participants. The prevalence of cytologically predicted high-grade SIL (HSIL, 17.9%) was lower than histologically diagnosed HSIL (31.7%, P < 0.001). The prevalence of composite-HSIL (detected by either method) was 37.7%. HPV16 prevalence was similar in men with HSIL by cytology (59.3%), HSIL by histology (51.0%), and composite-HSIL (50.0%). HPV16 prevalence was 31.1% in men with composite- atypical squamous cells suggestive of HSIL, to 18.5% in men with composite-low-grade SIL, to 12.1% in men with compositenegative results (P_trend < 0.001). Conclusions: Significantly more HSIL was detected when a composite cytology-histology endpoint was used. Increasing grade of composite endpoint was associated with increasing HPV16 prevalence. Impact: These data suggest that a composite cytology-histology endpoint reflects meaningful disease categories and is likely to be an important biomarker in anal cancer prevention.