Atypia of Undetermined Significance in Thyroid Fine-Needle Aspiration: Characterizing Cytopathologist Practice Patterns.
Paul A VanderLaan, Jeffrey F Krane, Edmund S Cibas. Brigham and Women's Hospital and Harvard Medical School, Boston, MA
Background: The standardized reporting framework established by The Bethesda System for Reporting Thyroid Cytopathology includes the category “atypia of undetermined significance” (AUS). This category should be used sparingly, with a proposed target rate near 7%. As the usage characteristics of this category are not well understood, the baseline AUS utilization rates over a five-year period were analyzed in anticipation of providing individual cytopathologist feedback.
Design: A customized report was written for the laboratory information system (LIS) that displays the category breakdown of thyroid fine needle aspiration (FNA) interpretations for the entire laboratory and for individual cytopathologists over a specified time period. With this report, a retrospective review of all thyroid FNAs from 1/05 to 12/09 was performed. All cases were reported using a six-tiered Bethesda-like diagnostic system. Results were compiled for individual cytopathologists, stratified by year, and correlated with histologic outcome when available.
Results: Seven cytopathologists evaluated a total of 5327 thyroid FNAs over this five-year period. An AUS diagnosis was rendered on 595 (11.2%) cases. Although the overall annual AUS rate for the laboratory remained relatively constant over this time period (range 9.9-12.4%), significant variability in AUS usage was seen not only between cytopathologists (individual averages: 6.1-18.7%) but also for individual cytopathologists over time (SD range: 1.4-4.0 percentage points). The AUS rate was unrelated to the experience of the cytopathologist. Correlation with histologic outcome data demonstrated an inverse relationship between the frequency of AUS and malignant outcome: the higher the AUS diagnosis rate, the lower the rate of malignancy (linear regression: R2=0.46, p<0.05).
Conclusions: This study demonstrates that, in the absence of directed feedback, AUS usage is highly variable and often exceeds the recommended target of 7%. In addition, high AUS rates are not necessarily related to any inexperience on the part of the cytopathologist, and high AUS use is likely due to overcalling benign FNAs. Looking forward, the application of recently defined diagnostic criteria for AUS, along with periodic cytopathologist feedback, could help achieve a lower target for this category. Customized LIS reports displaying category breakdown of thyroid FNA interpretations for individual cytopathologists over a specified time period will likely be useful for this purpose.
Tuesday, March 1, 2011 11:15 AM
Platform Session: Section F, Tuesday Morning