Background:  Although rare in the general community, anal cancer is now the most common non-AIDS defining cancer amongst the HIV-infected community in Australia, with rates are as high as 137/100,000 in HIV-infected Men who have Sex with Men (MSM). In order to investigate the potential role of anal cytological screening, we conducted a prospective study of HIV-infected MSM attending a HIV clinic in Sydney. Men with significant cytological abnormalities were then referred for High Resolution Anoscopy (HRA).

Methods:  Self-collected anal cytological samples were obtained using moistened Dacron swabs and then eluted into Thinprep^TM vials for subsequent analysis. Men yielding a cytological result of Atypical Squamous Cells of Undetermined Significance (ASCUS), Atypical Squamous Cells – possible High grade (ASC-H) or High-grade Squamous Intraepithelial Lesions (HSIL) were then referred for HRA.

Results:  In the study, 196 men participated. The age range was 25 to 75 years (median 50 years), with a median duration of HIV infection of 15 years. The current median CD4 was 488 10^6/mL and their median CD4 nadir 213 10^6/mL; 91% were taking antiretroviral therapy at the time of assessment. A single self-collected anal cytological specimen was obtained from each participant, of which, 172 (89%) were technically satisfactory. Of the technically satisfactory, 45 (23%) were cytologically normal, 75 (38%) had Low-grade Squamous Intraepithelial Lesions (LSIL), 26 (13%) had ASCUS, 17 (9%) ASC-H, and 9 (5%) HSIL. Of the 52 men (30%) had significantly abnormal anal cytology, defined as ASCUS, ASC-H and HSIL. 50 men underwent HRA and two men declined. Two men (4%) had no visual abnormalities and 48 (96%) men were biopsied. No person was diagnosed with anal cancer. High grade dysplasia (HSIL) was confirmed on biopsy in 29 (58%) of the 48 men who had undergone HRA. Thus, overall, severe dysplasia was detected in 29 (14.7%) of 196 screened men.

Conclusions: Self-administered cytological screening yielded technically satisfactory results in most men and identified high rates of significant anal dysplasia. Our estimate of the prevalence of HSIL is likely to represent an underestimate, as neither anal cytology nor HRA are 100% sensitive at detecting these abnormalities. Closer monitoring of these men is indicated until a clearer understanding of progression and regression rates is established. Interventions designed to prevent progression of HSIL to anal cancer need to be urgently evaluated.