Interobserver variability in subclassification of squamous intraepitheliallesions - Results of the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytology

Objective.-To determine whether, on a national cytology proficiency test, a competent cytologist can consistently distinguish grades of squamous intra epithelial lesions, Design.-Results for low- and high-grade squamous intraepithelial lesion ref erenced slides from the College of American Pathologists Interlaboratory Co mparison Program in Cervicovaginal Cytology for 1996 and 1997 were analyzed including educational, nongraded vs graded validated slides. Results.-The discrepant rate between low- and high- grade lesions ranged fr om 9.8% to 15% for cytotechnologist, pathologist, laboratory, and all respo nses. There was a statistically significant difference in performance on gr aded, validated slides vs educational slides with better performance on val idated slides. Conclusion.-This significant interobserver variability in subclassification of squamous lesions should be considered in management guidelines for abno rmal Papanicolaou test results and implementation of national cytology prof iciency testing.