Interobserver Agreement Using the New Bethesda System for Reporting Thyroid Cytopathology.
Teresa A Duran, Maria Policarpio-Nicolas, I-Tien Yeh, Thomas J Prihoda, Philip Valente. The Univeristy of Texas Health Science Center at San Antonio
Background: The recently proposed Bethesda System for Reporting Thyroid Cytopathology provides a uniform system for reporting the results of thyroid fine needle aspiration (FNA). Six diagnostic categories correspond to increasing risk of malignancy. The first three categories (non-diagnostic or unstatisfactory, benign, and atypia of undetermined significance or follicular lesion of undetermined significance) have lower risks of malignancy and are managed by clinical follow up or repeat FNA. The latter three categories (follicular neoplasm or suspicious for a follicular neoplasm, suspicious for malignancy, and malignant) have higher risks of malignancy and are clinically managed by surgical lobectomy or near-total thyroidectomy. The objective of this study was to report interobserver diagnostic variability. The precise agreement was evaluated as was practical agreement based on segregation of categories in two groups based on clinical management, i.e. clinical follow up-repeat FNA vs. surgical excision.
Design: A computer search of all thyroid lesions diagnosed by FNA from Jan 2008 to Dec 2009 was performed. These cases were reviewed independently by three pathologists and classified using the Bethesda System. Each category was given a gradient from 1-6 beginning with 1: Non-diagnostic, 2: Benign, 3: Atypia of undetermined significance, 4: Follicular Neoplasm, 5: Suspicious for Malignancy, and 6: Malignant. The pathologists were blinded to the clinical data, prior cytology diagnosis and subsequent surgical pathology findings. Interobserver variability was studied with respect to an precise agreement among all three pathologists and practical agreement in categories 1-3 vs 4-6, which would result in different patient management.
Results: A total of 79 cases classified utilizing the Bethesda System showed the following results: only 39.2% (31/79) cases had perfect agreement, but 65.8%(52/79) had practical agreement. The majority of cases with perfect agreement 64.5% (20/31) were for the benign category. Categories with the least absolute agreement include atypia of undetermined significance, follicular neoplasm and suspicious for malignancy each with only one case of absolute agreement 3.2% (1/31). A mean maximum difference of raters over 79 cases is 1.06+/- SE 0.11(p <0.01).
Conclusions: Not surprisingly, there is poor agreement of specific diagnostic categories among pathologists. Practical agreement relating to patient management is significantly better. Diagnostic agreement is likely to improve with increasing experience in the use of the Bethesda System.
Wednesday, March 2, 2011 1:00 PM
Poster Session VI # 59, Wednesday Afternoon