Diagnostic Validity of Ultrasound-Guided Fine Needle Aspiration Cytology in the Evaluation of Thyroid Swellings

Abstract

Background: Thyroid nodules are frequently encountered in clinical practice, and differentiating benign from malignant lesions is essential for appropriate management. FNAC (Fine Needle Aspiration Cytology) is the standard diagnostic technique; however, conventional palpation-guided FNAC may produce inadequate samples and false-negative results. Ultrasound-guided FNAC allows precise localization of thyroid nodules and targeted sampling, potentially improving diagnostic accuracy while reducing unnecessary surgeries and treatment costs. This study evaluated the diagnostic validity of ultrasound-guided FNAC compared with conventional palpation-guided FNAC in patients with thyroid swellings.

Methods: A diagnostic test evaluation (cross-sectional) study was conducted over one year in the Department of General Surgery, Government Medical College, Thrissur, Kerala. Ninety-six patients with clinically diagnosed thyroid swellings were randomly allocated into two groups: 48 underwent ultrasound-guided FNAC and 48 underwent conventional palpation-guided FNAC before thyroid surgery. Histopathological examination of surgical specimens served as the reference standard. Data were analyzed using SPSS, and sensitivity, specificity, PPV (Positive Predictive Value), NPV (Negative Predictive Value), and diagnostic accuracy were calculated.

Results: Among the 96 participants, 81 (84.4%) were females and 15 (15.6%) were males, with a mean age of 42.69 ± 11.3 years. Histopathology confirmed thyroid malignancy in 24 patients. Ultrasound-guided FNAC demonstrated a sensitivity of 90.9%, specificity of 97.3%, PPV of 90.9%, NPV of 97.3%, and diagnostic accuracy of 95.83%. In comparison, conventional palpation-guided FNAC showed a sensitivity of 53.84%, specificity of 94.28%, PPV of 77.77%, NPV of 84.61%, and diagnostic accuracy of 83.33%.

Conclusion: Ultrasound-guided FNAC is a superior diagnostic modality for evaluating thyroid swellings. It significantly improves sensitivity, diagnostic accuracy, and positive predictive value while reducing false-negative results compared with conventional palpation-guided FNAC. Routine use of ultrasound guidance is recommended wherever available to optimize the diagnosis and management of thyroid nodules.