Additional Value of Pertechnetate Scintigraphy to American College of Radiology Thyroid Imaging Reporting and Data Systems and European Thyroid Imaging Reporting and Data Systems for Thyroid Nodule Classification in Euthyroid Patients.

Thyroid nodules are common yet remain a diagnostic challenge. While ultrasound and Thyroid Imaging Reporting and Data Systems (TIRADS) are accepted as standard, the use of thyroid scintigraphy in euthyroid patients is debated. The European Association of Nuclear Medicine advocates it, whereas the American Thyroid Association and European Thyroid Association do not. However, it has not been evaluated whether scintigraphy adds value to TIRADS in a multimodal approach. Our study addresses this gap by assessing the impact of integrated pertechnetate scintigraphy on TIRADS accuracy. The diagnostic performance of ACR-TIRADS, EU-TIRADS, pertechnetate scintigraphy, and multimodal models were retrospectively analyzed for 322 nodules (231 benign, 91 malignant) in 208 euthyroid patients with histopathology as a reference. Generalized estimating equations were used for statistical analysis. On scintigraphy, 210 nodules were hypofunctional, 99 isofunctional, and 13 hyperfunctional. The AUC for thyroid scintigraphy, ACR-TIRADS, and EU-TIRADS were 0.6 (95% CI: 0.55-0.66), 0.83 (95% CI: 0.78-0.88), and 0.78 (95% CI: 0.72-0.83). Integrating scintigraphy with ACR-TIRADS and EU-TIRADS slightly increased diagnostic accuracy (AUC 0.86 vs. 0.83, = 0.039 and AUC 0.80 vs. 0.78, = 0.008) and adjusted the malignancy probability for intermediate risk TIRADS categories, with iso- or hyperfunctioning nodules in ACR-TIRADS-TR4 or EU-TIRADS-4 showing comparable malignancy probabilities as hypofunctioning nodules in TR3 or EU-TIRADS-3, respectively. Integrating thyroid scintigraphy with ACR- or EU-TIRADS moderately improves diagnostic performance, potentially benefiting management, especially in complex cases like multinodular goiter or indeterminate FNA. Further research is warranted to validate these findings and explore their clinical implications.