Evaluation of the Nature of Thyroid Nodules by Duplex Ultrasound and Assessment of the Diagnostic Accuracy of TIRADS Classification

Abstract

Introduction: Ultrasound (US) is the primary modality used to assess the thyroid glands. However, the terminology used by the radiologist is not easy for clinicians to understand. Thyroid Imaging Reporting and Data System (TIRADS) classification is the best attempt to facilitate better communication between the radiologist and clinicians. Aim: To assess the Thyroid Ultrasonography (USG) characteristics which are highly suggestive of malignancy and to assess the reliability of TIRADS in the differentiation of malignant from benign thyroid nodules. Materials and Methods: The present study was an observational study conducted on 200 consecutive patients presenting for thyroid swelling and underwent ultrasound of the thyroid. USG features recorded were the internal component, echogenicity, margins, calcifications, shape and vascularity. Using the modified Russ classification, each nodule was classified into a TIRADS category (I, II, III, IVA, IVB and V) based on the US features. Sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) was calculated for each of the suspicious US features. The risk of malignancy for each category of TIRADS classification was determined. All the nodules underwent cytological confirmation. The threshold for statistical significance was set at 0.05. Results: Among the USG characteristics, spiculated margin, microcalcification and taller-than-wide shape had highest specificity for malignant nodules. Anechoic nodule, iso or hyperechogenicity, predominantly cystic nature, macrocalcification and peripheral vascularity had a high NPV for the malignancy. The maximum number of the patients belonged to TIRADS Grade 3. The PPV was 100% for Grade V malignant nodules followed by 75% for Grade IVB malignant nodules. There was significant difference between IVA and IVB malignant nodules with IV A having very low risk for malignancy and IVB and V having significantly higher risk for malignancy. Conclusion: There is no single ultrasound feature which can diagnose malignancy in thyroid nodules however, there are combinations of USG features that can strongly suggest the possibility of malignancy. TIRADS serves as a convenient classification system which can be easily understood by the clinicians and guide them to do biopsy of the TIRADS IV and V nodules, which have highest malignant risk, thus helping in better patient management.

Keywords

• fine needle aspiration cytology
• malignant
• thyroid nodule
• ultrasonography