Given signs and symptoms of hyperthyroidism are non-specific, thyroid studies may be completed to evaluate patients with vague complaints such as tachycardia in the emergency department (ED). We sought to determine how often a new diagnosis of hyperthyroidism was made in patients who underwent thyroid laboratory testing in the ED.

The primary outcome of this study was a new diagnosis in the ED, or in the following 30 days, of hyperthyroidism or thyrotoxicosis following ED thyroid laboratory testing.

This was a retrospective chart review study in a single ED of all patients who had a TSH or free T4 ordered from 2007 to 2018, or a TSH value below, or a free T4 higher than the local reference ranges. Patients with a diagnosis of hypothyroidism were excluded.

12,366 patients underwent thyroid laboratory testing, and 12,244 patients were included. Of included patients, 655(5.4%) had abnormal thyroid studies, and 95(0.8%) patients received a new diagnosis of hyperthyroidism or thyrotoxicosis. The sensitivity and specificity of tachycardia for the diagnosis of hyperthyroidism was 70%(95% CI 62% to 77%) and 62%(95% CI 61% to 63%), respectively; and the positive and negative likelihood ratios were 1.8(95% CI 1.7 to 2.0) and 0.5(95% CI 0.4 to 0.6), respectively.

This study suggests that thyroid laboratory studies may be best used for a focused assessment for thyroid disorders rather than a screening tool for patients with one symptom of hyperthyroidism.