Implementation of the bethesda system for reporting thyroid cytopathology: Interobserver concordance and reclassification of previously inconclusive aspirates

Abstract

Standardized diagnostic terminology was introduced by the Bethesda System for Reporting Thyroid Cytopathology (BSRTC) in an effort to bring uniformity to the reporting of thyroid cytopathology, provide more defined categories to enable clinical management, and minimize the number of inconclusive cases. Previous studies indicate that the BSRTC is a reliable and valid reporting system for thyroid cytology. This study was conducted to compare the concordance between observers with varying cytopathology experience when using the BSRTC, and to assess the impact on the number of inconclusive reports. A retrospective study was conducted in two parts. In the first part 415 thyroid aspirates were reviewed independently by three observers with different experience levels. The aspirates were reclassified according to BSRTC and agreement scores were calculated using kappa statistics. In the second part 39 inconclusive aspirates signed out previously, were recategorized according to BSRTC. Agreement level between the three observers using the BSRTC was strong (Fleiss' kappa score = 0.6561). Inconclusive cases could be categorized further with BSRTC; there was significant reduction in the number of inconclusive diagnoses (P < 0.001). Strong interobserver agreement with BSRTC indicates the ease with which the new system can be applied in regular reporting. Significant reduction in the number of inconclusive diagnoses results in better communication with the clinician and improved risk assessment for thyroid aspirates.