Radiological–pathological correlation of the British Thyroid Association ultrasound classification of thyroid nodules: a real-world validation study

To evaluate the real-world performance of the British Thyroid Association (BTA) U classification, specifically focusing on radiology–pathology correlation and to glean learning points. Adults undergoing a neck ultrasound for thyroid nodules were reviewed over a period of 1-year. Data including demographics, nodule characteristics, BTA grading, and cytology/histopathology were retrieved with a minimum 24-month follow-up. Of 1,225 graded nodules in 964 patients, cytology and/or histology were available for 300 (24%). 57 cancers were detected. Of 24 (2%) U5 nodules, 14 were malignant, of 51 (4%) U4, 22 were malignant, of 256 (21%) U3, 20 were malignant, and from 894 (73%) U2 nodules, one cancer was discovered. BTA U grading with fine-needle aspiration (FNA)/core biopsy achieved 96.5% sensitivity, 93.7% specificity, and 93.9% accuracy compared to excision. There was no association between nodule size and rate of malignancy. This is the first study to validate the use of the BTA U-grading system in UK clinical practice. The BTA U-grading system is a robust and reliable method of evaluating the risk of malignancy in thyroid nodules with a high negative predictive value. Key learning points gleaned from the study were accurate assessment of nodule echogenicity, careful evaluation of solid–cystic nodules, optimising ultrasound technique, and the low-risk nature of U3 nodules. •This study validates the BTA ultrasound grading system in clinical practice.•The BTA U system is a robust reliable method of excluding cancer in thyroid nodules.•Thyroid nodule size is a poor indicator of malignancy.•Echogenicity, mural nodule in cyst, and optimal technique are key considerations.•U3 nodules are accurately regarded as Low-Risk rather than Indeterminate.