25 Interobserver agreement in the evaluation of urine cytology for the detection of urothelial malignancy

Introduction:  Urine cytology is a test used to diagnose and monitor for urothelial malignancy. It is a biological test for which there is no gold standard. The diagnosis offered is based on the subjective interpretation by the cytopathologist viewing the slide. As in all biological systems for which there is no gold standard, the interpretation is subject to clinical disagreement and interobserver variation. The aim of this study is to evaluate the agreement between cytopathologists in the interpretation of urine cytology. Materials and Methods:  Two hundred urine cytology slides were collected over a six month period, from a busy metropolitan pathology firm. The series was made up of four categories, normal, atypical, suspicious for malignancy, and malignant. Each category contained fifty representative slides. The slides were reviewed by two independent reviewers as quality control and masked prior to been given randomly to four raters for assessment. The raters consisted of two screening scientists and two cytopathologists. Each rater received each slide in a random fashion and was asked to independently categorise the slide into one of the above categories. The level of agreement was analysed using Cohen weighted Kappa statistics. Results:  The interobserver agreement in the assessment of urine cytology by cytopathologits in the detection of urothelial malignancy is moderate using Cohen's kappa weighted statistics. Conclusions:  The interobserver agreement in the assessment of urine cytology by cytopathologists is moderate and as such should be born in mind when investigating patients for urothelial malignancy.