Morphologists overestimate the nuclear-to-cytoplasmic ratio

The Paris System for Reporting Urinary Cytology (TPS) has defined nuclear-to-cytoplasmic (N:C) ratio cutoff values for several of its risk-stratified diagnostic categories. However, because pathologists are not trained to recognize strict N:C ratio cutoff values, a previously designed survey was used to determine whether pathologists could accurately identify N:C ratios according to TPS standards.

Participants were instructed to estimate the N:C ratio of ideal (line drawing) and real (cell photograph) images presented via an online survey. Actual N:C ratios ranged from 0.3 to 0.8, and 3 answer choices were available: < 0.5, ≥ 0.5 and <0.7, and ≥0.7. The resulting data were analyzed to determine the accuracy and performance of the subgroups.

A total of 137 individuals completed the survey. Approximately 24.1% were cytopathologists, 18.2% were pathologists without formal cytopathology training, 18.2% were cytotechnologists, 24.1% were pathology residents, and 15.3% were nonmorphologists. Overall, 70.0%, 67.6%, and 93.3% of responses, respectively, were correct for images with an N:C ratio of < 0.5, ≥0.5 and < 0.7, and ≥0.7. For images with an actual N:C ratio < 0.5 and ≥0.5 and < 0.7, 30.0% and 25.0% of responses, respectively, overestimated the N:C ratio. Furthermore, for images with an N:C ratio of 0.4 and 0.6, > 40.0% of responses overestimated the N:C ratio. As a whole, morphologists were significantly more accurate than nonmorphologists (P = .030).

Morphologists tended to overestimate the N:C ratio, particularly at ratios close to TPS-recommended cutoff values. Additional training regarding N:C ratio estimation may help pathologists to adapt to this new system. Cancer Cytopathol 2016;124:669-77. © 2016 American Cancer Society.