Room for improvement: initial experience with anal cytology: observations from the College of American Pathologists interlaboratory comparison program in nongynecologic cytology.

CONTEXT Anal cytology is being used more frequently for anal cancer screening, yet many cytologists are unfamiliar with it. OBJECTIVE To describe the performance of anal cytology in the College of American Pathologists' Interlaboratory Comparison Program in Non-Gynecologic Cytology (CAP NGC) educational slide program during a 6-year time span, from 2006 to 2011, using participant responses (pathologist, cytotechnologist, and laboratory). DESIGN Concordance rates for the target diagnosis and general category for each slide challenge were analyzed. Four main factors were included in the analysis: (1) general category or specific responses, (2) program year from 2006 to 2011, (3) participant type (pathologist, cytotechnologist, or overall laboratory), and (4) preparation type (liquid-based or conventional). RESULTS Participants most frequently correctly classified negative for intraepithelial lesion or malignancy, low-grade squamous intraepithelial lesion, and herpes simplex virus infection, with concordance rates of 78.8%, 85%, and 80.2%, respectively. Performance on challenges with target diagnoses of high-grade squamous intraepithelial lesion (HSIL), squamous cell carcinoma, and ameba was poor, with concordance rates of 57.1%, 56.2%, and 41.5%, respectively. Significant improvement during the 6 years was seen in the concordance rates of participants' responses for low-grade squamous intraepithelial lesion challenges but not for HSIL. There was no significant difference in performance by slide preparation type. CONCLUSIONS The poor performance on anal cytology in the CAP NGC program, especially with regard to correct identification of HSIL and squamous cell carcinoma, indicates that there is a need for continued education about anal cytology.