Correlation of Fine Needle Aspiration Cytology and Histopathology in Thyroid Nodules: A Six‐Year Study at a Tertiary Public Laboratory in the Western Cape Province, South Africa

Résumé fourni par la source

BACKGROUND: Fine-needle aspiration cytology (FNAC) is the primary screening test for thyroid nodules. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) provides six diagnostic categories, each with an implied risk of malignancy (ROM). This study evaluated the performance of thyroid FNAC and the application of TBSRTC categories in a tertiary anatomical pathology service in South Africa. METHODS: This retrospective laboratory-based audit included all 1703 thyroid FNACs processed between January 2016 and December 2021. Procedural details such as palpation versus ultrasound-guided aspiration were not captured in the laboratory data set. TBSRTC category distribution was assessed, cytology-histology correlation was performed for 315 cases with histology, and ROM was calculated. Diagnostic accuracy metrics, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy, were calculated using dichotomized cytology and histology results. RESULTS: The mean proportion of FNAC reports that included a Bethesda category was 74.9%, and 854 (50.1%) cases were non-diagnostic (Category I). The overall ROM, including category I and category II, was 7.4% if cases of low-risk neoplasms were considered non-malignant. The ROM for Categories I to V was within the published TBSRTC ranges, while the ROM for Category VI was lower (81.8% vs. 86%-100%). The diagnostic accuracy was 54.8%, specificity 41.9%, sensitivity 73.4%, PPV 46.6%, and NPV 69.5%. CONCLUSION: The rate of non-diagnostic FNACs was higher than published estimates, suggesting the need for provider-training on ultrasound-guided FNAC, with rapid on-site evaluation for specimen adequacy. There is a need to explore the factors that impact FNAC test performance in our setting.

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