Radiological-pathological Correlation of the British Thyroid Association Ultrasound Classification of Thyroid Nodules: a Real-world Validation Study

Aim: 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.

Methods And Materials: 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.

Results: 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.

Conclusion: 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.