Rates of Detecting Thyroid Nodules Recommended for Biopsy with Ultrasound: Are All Indications Equal?

Background: The use of thyroid ultrasound increases yearly, adding to costs and over-detection of clinically irrelevant nodules. We investigated which indications most commonly prompt referral for thyroid ultrasound and the diagnostic utility by indication. Methods: We performed a retrospective observational cohort study of adults (≥18 years) undergoing an initial, dedicated thyroid ultrasound between 2017-2019 at a tertiary, academic center. Indicated reasons for referral were categorized into: suspected palpable nodule (SPN), compressive symptoms (CS), metabolic symptoms (MS), screening due to high-risk factors, follow-up of incidental finding on other imaging, and combination of factors. Percent of ultrasounds with an identifiable nodule and with a nodule recommended for biopsy was compared by indication. Separate logistic regression models were used to identify factors associated with finding any nodule and a biopsy-recommended nodule. Results: Among the 1739 patients included, the most common indication for thyroid ultrasound was SPN (40%), followed by incidental imaging (28%), CS (13%), combination (11%), MS (6%) and high-risk factors (2%). Overall, 62% of ultrasounds identified a nodule. Ultrasounds performed for incidental findings had the highest rate of nodule identification (94%), compared to 55%, 39%, and 43%, for SPN, CS, and MS, respectively (p