An Institutional Quality Assurance Study To Identify Factors Influencing Rates of Thyroid Bethesda System Categories among Cytopathologists
Sara E Wobker, Louise M Henderson, Jennifer S Cayless, Susan J Maygarden. University of North Carolina Hospitals, Chapel Hill, NC
Background: The Bethesda System for Reporting Thyroid Cytopathology (TBS) recommends a six category scheme for thyroid FNAs. Importantly, the new Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/FLUS) category was introduced in 2008. We compared the rates of each TBS category and studied factors that may influence the rate of AUS/FLUS among 6 board-certified cytopathologists at our institution with lengths of practice ranging from 2-25 years.
Design: We identified all thyroid FNAs (n=927) from January 2010-September 2012 using CoPath. We then searched for corresponding surgical excisions to determine malignancy rates. Rates of TBS category and malignancy rates were calculated for each cytopathologist. We then dichotomized cytopathologists into those who began practice prior to the introduction of AUS/FLUS (pre-TBS) and those who began after (post-TBS). We compared the use of AUS/FLUS between pre- and post-TBS using the chi-square test. To assess if the malignancy rate of AUS/FLUS differed among the two groups, we computed Fisher's exact test.
Results: The overall laboratory rates were 9.7% unsatisfactory (U), 63.6% benign (B), 14.2% AUS/FLUS, 5.6% follicular neoplasm/suspicious for follicular neoplasm (FN/SFN), 2.9% suspicious for malignancy (SM) and 4.0% malignant (M). Individual pathologist rates ranged from 6.5-11.5% U, 56.9-75.4% B, 4.2-23.9% AUS/FLUS, 2.6-10.2% FN/SFN, 1.5-3.7% SM and 1.7-7.7% M. There were significant differences between pathologists in use of TBS categories (p = 0.0005). Only 1 pathologist classified <7% of samples as AUS/FLUS. There was a significantly lower rate of AUS/FLUS among pathologists who began practice before TBS (pre-TBS rate 10.3%, post-TBS rate 17.4%, p=0.0016). We identified 173 cases with follow-up histology (18.7%). Omitting unsampled incidental papillary microcarcinomas, overall laboratory malignancy rates by TBS category were 0% U, 6.25% B, 10.9% AUS/FLUS, 35.1% FN/SFN, 75.0% SM, 100.0% M. Malignancy rates for the AUS/FLUS category were 20.0% for pre-TBS pathologists vs. 5.7% for post-TBS (p=0.1755).
Conclusions: Board certified pathologists at our institution show significant differences in their use of TBS categories. Pathologists who began practice post-TBS had a higher rate of use of the AUS/FLUS category than pre-TBS pathologists, but differences in malignancy rates for these two groups were not statistically different.
Tuesday, March 5, 2013 1:00 PM
Poster Session IV # 84, Tuesday Afternoon