Pap smears may not be an accurate predictor of high grade precancerous anal lesions that can lead to the development of anal cancer, according to a US study published in the May 15th edition of Clinical Infectious Diseases, which is now available on-line. Recently there has been much discussion about the value of offering Pap smears to HIV-positive gay men who have anal HPV infection, particularly as several studies have indicated that not only are HIV-positive men at an increased risk of anal cancer, but that HAART does not appear to reduce the risk. These findings underline the importance of closely monitoring individuals with abnormal anal cells.
Investigators from Boston paired the cytology results from 153 gay men attending an anal dysplasia clinic with histology results obtained from high resolution anoscopy. A total of 100 men (65%) were HIV-positive and the remaining 53 (35%) were HIV-negative. Cytology samples were obtained by swabbing or scraping the anus and rectum, whilst the histology samples were obtained by obtaining a tissue sample by biopsy.
Analysis of the paired results indicated that Pap cytology tests were not an accurate predictor of high grade precancerous anal lesions (anal intraepithelial neoplasia, AIN), and that a third of the Pap smears categorised by cytology as “low-grade” (AIN I) were in fact found to be “high-grade” (AIN III) when the histology results from an anal biopsy were studied.
The investigators note that their data “independently confirm a substantial incidence of histologically proven high-grade anal dysplasia in [gay men] who present with minimally abnormal anal Pap smear findings.” No association between the presence of high-grade lesions and HIV status was found.
The investigators conclude that “abnormal anal cytological findings of any grade should suggest the possibility of high-grade histological findings.”
Further information on this website
French study shows HAART no benefit against HPV or pre-cancerous anal lesions - news story
Anal cancer bad news for HIV-positive gay men even in HAART era, but incidence is rare - news story
Panther LA et al. High resolution anoscopy findings for men who have sex with men: inaccuracy of anal cytology as a predictor of histologic high-grade anal intraepithelial neoplasia and the impact of HIV serostatus. Clinical Infectious Diseases 38 (on-line edition), 2004.