The efficacy of bethesda system for prediction of thyroid malignancies - A 9 year experience from a tertiary center

Introduction: The best initial investigation for thyroid nodule is fine needle aspiration (FNA). Bethesda System is an international standardized system of reporting thyroid nodules and recommends subsequent management. Every institution should assess the risk of malignancy in each category to avoid unnecessary thyroid surgeries, with this aim we conducted a review at our center to calculate risk of malignancy in each category. Materials and Methods: Retrospective 9-year (2009–2018) review of thyroid FNAs done at a tertiary care Centre. The FNA was stratified according to The Bethesda System. Histopathology reports of the operated cases were used to evaluate the cytology for diagnostic accuracy. Results: There were 495 patients who underwent thyroidectomy. The mean age of the cohort was 42.51 +/- 13.2 years and 387 (78.2%) were females. The frequency of Bethesda categories I, II, III, IV, V, and VI were 9.1%, 55.6%, 16.4%, 6.5%, 9.3%, and 3.2% respectively. Malignancy rate in operated thyroid nodules were 37.8%, 8.4%, 33.3%, 50.0%, 89.1%, and 100% for Bethesda categories I to VI, respectively. The sensitivity, specificity, negative predictive value and positive predictive value and their 95% CIs were calculated as 81.30 (73.28 – 87.76%), 77.06 (72.12 – 81.51%), 91.64 (88.3 – 94.1%) and 57.14 (51.79 – 62.33%). The overall diagnostic accuracy was 78.22 (74.12 – 81.95%). Conclusions: All the Bethesda categories showed greater malignancy risks than other reported studies. Knowledge of local rates of malignancy is important to accurately predict the risk of malignancy even when reported with internationally accepted nomenclature like the Bethesda System.