Abstract
Subacute thyroiditis (SAT) is an inflammatory thyroid disorder characterized by neck pain, transient thyrotoxicosis, and a self-limiting clinical course. Accurate diagnosis is essential to avoid unnecessary treatment for hyperthyroidism. While the radioiodine uptake (RAIU) scan remains the diagnostic gold standard, its use is limited by radiation exposure, cost, and availability. High-resolution grayscale and color Doppler ultrasonography offer a non-invasive alternative, but their diagnostic accuracy compared with RAIU remains under investigation. To determine the diagnostic value of combined grayscale and color Doppler ultrasonography in detecting subacute thyroiditis compared with thyroid radioiodine uptake scanning. This cross-sectional diagnostic accuracy study included 28 patients with suspected SAT who underwent both ultrasonography and RAIU scanning. Characteristic sonographic features—including ill-defined heterogeneous hypoechoic areas and decreased vascularity—were recorded. Diagnostic indi-ces such as sensitivity, positive predictive value (PPV), and accuracy were calculated against the RAIU reference standard. Ill-defined heterogeneous hypoechoic areas were observed in 85.7% of patients and demonstrated the highest diagnostic performance (sensitivity 100%, accuracy 96.4%). Decreased or absent vascularity within these regions was present in 78.6% of cases. The combined grayscale and color Doppler assessment achieved an overall sensitivity of 96.3%, PPV of 96.3%, and accuracy of 92.8% compared with RAIU. Combined grayscale and color Doppler ultrasonography provides a reliable, accurate, and accessible diagnostic tool for subacute thyroiditis. Given its non-invasive nature and strong agreement with RAIU findings, ultrasonography can be considered a practical first-line imaging modality for evaluating patients with suspected SAT.