Intralaboratory reproducibility of interpretation of Pap smears: results of an experiment.

One hundred and twenty Pap-smears were examined by 3 cytotechnologists on two occasions in the Legnano Hospital Cytologic Center. A 10-category classification system was used. Chance-adjusted overall and category-specific agreement was estimated (Cohen's unweighted kappa-statistics) within and between cytotechnologists. Mean K for the Center, weighted for precision, was 0.432, S.E. 0.029 (between cytotechnologists). The most reproducible categories (between cytotechnologists) were "9: malignant cells" (K = 0.683) and "1: normal" (K = 0.533); the least reproducible categories were "4: endocervical metaplastic cells" (K = 0.024) and "8: severe squamous dysplasia CIN III" (K = 0.227).