Accuracy of High Resolution Ultrasound Examination for Prediction of Malignancy Thyroid nodules: FNAC or HP as reference standards

Abstract

Background: Thyroid nodules comprise a diagnostic challenge mainly because of the need to exclude thyroid malignancy. Approximately, 4% is an estimated prevalence of thyroid nodule on palpation with 15% lifetime risk of developing a thyroid nodule. Objective: To provide importance of sonographic and doppler criteria for differentiation between benign and malignant solid thyroid nodules and their correlation with Fine-needle aspiration cytology (FNAC) or histopathology (HP). Methods: A prospective study of 103 patients (January 2012 to June 2013) selected from radiology department of Dr.Ziauddin Hospital Karachi who came for ultrasound (US) of thyroid with clinical diagnosis of thyroid nodule followed by FNAC. Presence of malignant features were taken as positive finding for malignancy. The results of US were compared with FNAC/HP and diagnostic accuracy was calculated. Results: Out of 103 cases, 80 were labeled as true positive because US and FNAC results were positive for malignancy while the 2 were false positive as US shows malignant features but FNAC results were negative. 8 patients were labeled as true negative because US and FNAC were negative for malignancy and 13 patients were false negative because US results were negative for malignancy but FNA results were positive. The overall sensitivity and specificity of US was 86.0% and 80.0% respectively. Similarly the positive predictive value (PPV) was 97.5%, negative predictive (NPV) was 38.0% and diagnostic accuracy was 85.43% when compared with FNAC/HP results. Conclusion: Although US is an important tool for prediction of thyroid nodule malignancy, it cannot substitute FNAC/HP for accurate detection for malignancy. However, it can reliably anticipate the suspicion lesions which need intervention on priority basis. Key Words: Fine-needle Aspiration Cytology, Nodule, Thyroid, Ultrasound.