Role of ultrasound scan and fine needle aspiration cytology on pre-operative assessment of suspicious thyroid nodules in a resource-limited setting

Introduction: Although the prevalence of thyroid tumor is about 7% in the general population, the malignancy rate is approximately 5% among thyroid tumors. This emphasizes the need for effective preoperative diagnostic methods for proper patient management. Methods: A descriptive cross-sectional study was conducted at Colombo South Teaching Hospital and the Department of Pathology, University of Sri Jayewardenepura, Sri Lanka. Patients with radiologically suspected malignant thyroid nodules (n=107) were enrolled. fine needle aspiration cytology (FNAC) was performed under ultrasound scan (USS) guidance by an experienced consultant radiologist. Direct smears and cell block preparations were prepared from FNAC specimens. Smears were reviewed by two independent pathologists. USS and FNAC findings were reported according to Thyroid Imaging Reporting and Data System (TIRADS) system and Bethesda system, respectively. Descriptive statistics were expressed as frequencies and percentages. Diagnostic performance of USS and FNAC was assessed using receiver operating characteristic (ROC) curve. Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated. Results: The Majority (79.4%) were females. Age ranged from 15 to 76 years (47.3±12.89). Malignant risk prediction of 77% was observed in TIRADS system. Malignant risk of 17.9%, 37.5%, and 87.5% were reported respectively for TIRADS 4a, 4b, 4c categories while TIRADS 5 reports a risk of 60.0%. Sensitivity, specificity, NPV, and PPV of FNAC were 88.9%, 87.5%, 96%, and 70% respectively compared with the histology results. Conclusion: Bethesda system cytology reporting and radiologic TIRADS classification are important preoperative diagnostic tools for identifying suspicious thyroid nodules in resource-limited setting. FNAC was a better diagnostic test compared to USS for evaluating thyroid nodules.