EP54 – Accuracy of Fine Needle Aspiration of Thyroid Nodules in New Zealand; Are Our Rates Comparable and What Influences Our Accuracy?

      Barnard, Jon1; Clinick, Tara2; Harper, Simon3 1Department of General Surgery, Taranaki Base Hospital, New Plymouth, New Zealand 2Department of General Surgery, Wellington Hospital, Wellington, New Zealand 3Department of General Surgery, Wellington Hospital, Wellington, New Zealand   Background/Purpose: Fine Needle Aspiration (FNA) is the recognised gold standard for initial evaluation of a thyroid nodule. Recent studies dispute the accuracy of risk stratification of FNAs by The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC)1-3 showing unexpectedly higher malignancy rates in some categories. It follows that if risk is higher than believed in certain Bethesda categories, operative management may be less appropriately utilised than previously thought. The purpose of the current study was to assess the accuracy of FNA of thyroid nodules, and determine the factors that influence that accuracy. Methods: All thyroid nodule samples classified by TBSRTC since its introduction in our regional laboratory were analysed. Accuracy was determined from surgical histopathology. Logistic regression analysis was performed to investigate factors that influence both the rate of malignancy and rate of re-biopsy. Results: The present study demonstrated rates of malignancy similar to those in international meta-analyses4, with the exception of a higher malignancy rate in Bethesda IV nodules. Risk of malignancy appeared to be associated with nodule size and was predicted by number of suspicious ultrasonographic features5.  Surgeons had 2.310 times higher odds of a repeat FNA than radiologist. Discussion/Conclusion: TBSRTC has excellent predictive value for benign and malignant disease, and with the exception of Bethesda IV nodules, TBSRTC appears to be accurate. Further investigation is required to investigate the malignancy rates in Bethesda IV nodules, as well as the apparent discrepancy in accuracy of FNA when performed by a surgeon compared to a radiologist.   References:
    1. Deniwar, A. Hambleton, C. Theti, T. Moroz, K. Kandil, E. Examining the Bethesda Criteria Risk Stratification of Thyroid Nodules. Pathology- Research and Practice. 2015; (211); 345-348
    2. Ho, AS. Sarti, EE. Jain, KS. et al. Malignancy Rate in Thyroid Nodules Classified as Bethesda Category III (AUS/FLUS). Thyroid. 2014; 24(5): 832-839.
    3. Mathur, A. Najafian, A. Schneider, EB. Zeiger, MA. Olson, MT. Malignancy Risk and Reproducibility Associated with Atypia of Undetermined Significance on Thyroid Cytology. Surgery. 2014; 156(6): 1471-1476.
    4. Bongiovanni, M. Spitale, A. Faquin, WC. Mazzucchelli, L. Baloch, ZW. The Bethesda Criteria for Reporting Thyroid Cytopathology: A Meta-Analysis. Acta Cytologica. 2012; 56: 333-339.
    5. Cooper DS, Doherty GM, Haugen BR, et al. Revised American Thyroid Association Management Guidelines for Patients With Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid. 2009; 19: 1167–1214.


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