A serum thyroid hormone metabolite test for molecular diagnostic evaluation of thyroid nodules

This was a cohort study of 1,663 subjects (1196 women, 467 men; median age 48 years, IQR 37-57) with thyroid nodules recruited from 2020 to 2025 in five tertiary medical centers. Cytological/histopathological diagnoses were established by an independent review committee, and preoperative serum thyroid hormone metabolites (THMs) were tested using liquid chromatography tandem mass spectrometry. A diagnostic model on this serum THM test to distinguish between differentiated thyroid cancer (DTC) and benign thyroid nodule (BTN) was trained on 872 retrospective subjects (454 DTC and 418 BTN), followed, prospectively, by model validation on 392 subjects (195 DTC and 197 BTN) and a second validation on 399 subjects (300 DTC and 99 BTN). Following successful diagnostic model training, the model validation demonstrated a diagnostic specificity of 99.5% (196/197), sensitivity of 92.3% (180/195), positive predictive value (PPV) of 99.4%, negative predictive value (NPV) of 92.9%, and diagnostic accuracy of 95.9% (95% CI, 90.8 to 100.0%) for DTC. Combination of the two validation cohorts showed a diagnostic specificity of 99.7% (295/296), sensitivity of 92.1% (456/495), PPV of 99.8%, NPV of 88.3%, and diagnostic accuracy of 94.9% (95% CI, 91.5 to 98.0%) for DTC. The test on indeterminate Bethesda categories III-IV (139 DTC, 87 BTN) showed a diagnostic specificity of 100.0% (87/87), sensitivity of 93.5% (130/139), PPV of 100.0%, NPV of 90.6%, and diagnostic accuracy of 96.0% (95% CI, 89.2 to 100.0%) for DTC. This study develops a novel molecular blood test of serum THMs for preoperative diagnostic evaluation of thyroid nodules, which displays a high PPV and decent NPV with an excellent overall diagnostic accuracy for DTC.