A pragmatic assessment of the British Thyroid Association "U classification" of thyroid nodules with a focus on their follow-up.

Aim: To assess the predictive value of the U classification and the significance of follow-up ultrasound in those managed conservatively.

Materials And Methods: A retrospective observational study was carried out among 1,465 patients who underwent thyroid ultrasound in 2016 at a teaching hospital in UK. Details regarding U classification of nodules, cytology, histology in patients who underwent surgery, and follow-up ultrasound in those managed conservatively were obtained.

Results: Thyroid surgery was performed in 129 patients of which malignancy was seen in 35 (27.1%). The proportion of patients with cancer in U1-U5 categories were 0%, 13.6%, 30.4%, 40%, and 100%, respectively (Fisher's exact test p=0.001). There was no significant difference in U stage, cytology, or histology between incidental and symptomatic nodules. Among patients who did not undergo surgery 5% of U1, 14.6% of U2, 75% of U3, and 71.4% of U4 underwent repeat ultrasound. Radiological progression in nodule size was seen in 4.2% of U1, 1.9% of U2, 0% of U3, and 40% of U4 nodules at median duration of 306, 439, 274, and 748 days, respectively.

Conclusions: U classification is reliable in risk-stratifying thyroid nodules. Patients with benign nodules without high-risk features do not require follow-up. The interval between scans in patients with indeterminate nodules can be extended to a period of 6-12 months.