Interobserver reproducibility of The Paris System of Reporting Urine Cytology on cytocentrifuged samples

The Paris System of Reporting Urine Cytology aims to screen samples for HGUC and to provide a universally acceptable reporting format for urine cytology specimens. However, studies detailing the reproducibility of this system, especially on cyto-centrifuge preparations, are lacking.

149 voided urine samples received in Department of Pathology were reviewed independently by five cytopathologists. To estimate the overall agreement, Gwet's AC and AC1statistics between each pair of raters were used. To measure the random error component, polychoric correlations were used. To assess the systematic error, Friedman test was used.

There was moderately good inter-rater agreement between the raters. Gwets AC2 ranged between 0.67 and 0.89 for the classification of the cases once the sample was found adequate for assessment, while the Gwet's AC1 ranged between 0.61 and 0.94 in assessing for adequacy. There were significant systematic differences between raters in their thresholds for the different categories as well as in differentiating between an adequate and inadequate sample (P value by Friedman test <.001). The association between pathologists was moderately high (polychoric correlations ranging from 0.67 to 0.93). In the majority (108 of 149, 72.5%) of the cases, the range of differences between raters were of one category or less, suggesting satisfactory agreement, but having large disagreements in minority.

The interobserver reproducibility for the Paris System is moderately good, and is suitable for adoption. It is limited by the lack of agreement as to what constitutes an adequate specimen and differing threshold for categorizing the lesions in differing groups.