Classification of cervical smears with discordance between the cytologic and/or histologic ratings.

The problems of diagnostic variability between certified cytotechnologists was studied. Three cytology laboratories submitted a total of 28 cervical smears that had a discordance between the cytologic and/or histologic ratings. Eight independent cytotechnologists provided blind readings on each slide, expressed as "absence of cervical intraepithelial neoplasia (CIN)" to "CIN III." The median rating was absence of CIN or CIN I for 8 slides, CIN II for 5 and CIN III for 15. With a kappa value greater than 0 reflecting agreement beyond chance expectation and a value of 0.40 indicating fair agreement, the kappa value for 8 X 28 ratings was 0.36 (P = .0001), with a 90% confidence interval (CI) between 0.34 and 0.37. The kappa value was 0.14 (P = .10), with a 90% CI between 0.10 and 0.18, on a subsample of nine smears with two or more positive cytology diagnoses but a negative histology. Sixteen of the 28 slides represented cases of histologically proven cancer. Treating cytologic diagnoses of CIN II and CIN III as positive, the sensitivity of the cytologist with reference to histology varied between 71% and 86% while the specificity ranged from 18% to 62%. The positive predictive value was 1/2.5 to 1/1 and the negative predictive value was 1/6 to 1/1. The predictive power (true positives/false positives) ranged from 1.0 to 2.2. The cytodiagnosis of these cervical smears from cases of discordance thus exhibited limited reliability. Standardization of the relevant cytologic knowledge and its routine application is needed to improve the level of performance.

Standardized model for diagnosing cervical carcinoma in situ based on the cytologic signs.

An attempt was made to optimize the recognition of cervical intraepithelial carcinoma in situ (CIS) by the adoption of a standard set of rules derived from a case-control study of 50 histologically confirmed incidence cases of CIS and a simple random sample of 100 controls from the same mass screening population examined between 1977 and 1984. One cytotechnologist screened the slides for all occurrences of a standard set of classic cytopathologic signs. Chromatin clumping, dyskeratosis, anisonucleosis and an increased nuclear-cytoplasmic ratio in cells from the deep layer and chromatin clumping and anisonucleosis in cells from the superficial layer showed an association with the diagnosis of CIS, in decreasing order of magnitude. These variables make up a binary discriminant model; adding vacuolization, anisocytosis, prominent nucleoli and multinucleation to this model did not appear to improve its discriminatory power. The discrimination function accommodates any a priori judgment regarding the probability and utility of diagnostic outcomes. Cytologists normally manipulate the probabilities and utilities intuitively; the model requires the translation of intuitive judgments into quantitative estimates. For example, in our cytology laboratory, the CIS pick-up rate is approximately 1 per 1,000 smears; a 1:1,000 negative utility ratio of a false positive versus a false negative is thus used in our model. Given this, our model has a sensitivity of 86% and a specificity of 96% upon reclassification, and its predictive power (true positives/false positives) is 21.5. This standardized cytodiagnosis model is relevant to any local diagnosis-specific probability and utility estimates.