Performance of Candida—Fungal-Induced Atypia and Proficiency Testing: Observations From the College of American Pathologists Proficiency Testing Program

Abstract

Candida may elicit cellular changes on otherwise negative screening Papanicolaou tests that may be misinterpreted as atypical squamous cells of undetermined significance. Although these changes have been correctly interpreted in the educational program of the College of American Pathologists, the Interlaboratory Comparison Program in Gynecologic Cytology, the performance of negative slides with Candida faltered when the same field validated slides were included in proficiency testing (PT). To identify the performance differences of negative for intraepithelial lesion (NILM) Candida challenges before and after PT. We compare the performance of NILM College of American Pathologists slides with Candida as a single reference diagnosis, prior to PT (1991-2006) and after PT (2006-2007). There were 147,186 responses for slides with NILM Candida from the College of American Pathologists programs from 1991 through 2007. After PT, 79.7% of incorrect participant responses identified Candida as Category C (low-grade squamous intraepithelial lesion), whereas prior to PT only 59.5% of the incorrect diagnoses were low-grade squamous intraepithelial lesion (P < .001) in the field-validated component of the program. Validated Candida slides performed significantly more poorly in PT (97.2%) than prior to PT (98.3%) (P < .001). Candida challenges performed better in the educational component post-PT (98.3% versus 97.2%; P < .001). Cytotechnologists (97.9%) identified Candida more frequently than pathologists (97.3%) (P < .001) and ThinPrep preparations performed the best of all preparation types. Proficiency testing adversely affects the performance of participants in the identification of NILM Candida. Slides with Candida are more likely to be identified as low-grade squamous intraepithelial lesion in a PT exercise. Misidentification is not due to lack of recognition but most likely an attempt of test takers to optimize their likelihood of passing the examination.