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Clinician-collected specimens superior to self-collected in detecting anal cancer
Cytology screening may be an important tool in identifying anal intraepithelial neoplasia in men who are HIV-positive and have sex with men, according to recent data.
Researchers from the University of California at San Francisco and Oregon State University in Oregon conducted a cross-sectional study of men who have sex with men to compare the sensitivity of self-collected vs. clinician-collected anal cytology specimens in the detection of biopsy-confirmed anal intraepithelial neoplasia.
The study included a community-based sample of 126 men from the Urban Men’s Health Study. The researchers measured the prevalence of HPV and anal intraepithelial neoplasia among participants.
Anal intraepithelial neoplasia was confirmed by biopsy and diagnosed in 57% of men who were HIV-positive and 35% of men who were HIV-negative (P=.04). Eighty percent of participants provided self-collected specimens.
Cytology was more sensitive in detecting anal intraepithelial neoplasia when specimens were clinician-collected in men who were HIV-positive (90%) and HIV-negative (62%), compared with self-collected specimens (75% for HIV-positive and 48% for HIV-negative).
Specificity of cytology was also superior for clinician-collected samples in men who were HIV-positive (64% vs. 50% when self-collected). However, the specificity was similar in men who were HIV-negative: 86% for self-collected vs. 85% for clinician-collected, according to the researchers.
Ann Intern Med. 2008;149:300-306.
This is small cross-sectional study attempting ultimately to assess the broad applicability of self-collected anal cytology specimens as a screening tool for high grade AIN, a precursor for anal SCC, to avoid the more invasive and time/cost-intensive anoscopy. The interpretation of the study is difficult to generalize on the basis of this small, geographically confined group of homosexual and bisexual men at high risk of anal cancer, as other potentially confounding factors such as underlying HPV infection (eg condylomas), differential high risk activity/frequency of sexual activity and the clinical control of HIV or AIDS/HAART administration are not addressed. Unfortunately, the sensitivity of a self-procured specimen is lower than the clinician-collected approach, and with a high false negativity, making it unacceptable as a screening test. Hence, an experienced clinician-collected anal cytology, which also provides additional visual and palpable evaluation and an anoscopy should remain the standard of care in high risk patients.
– Ki Y. Chung, MD
Medical oncologist, Gastrointestinal Oncology Service, Memorial Sloan-Kettering Cancer Center