Peak Systolic Velocity of Superior Thyroid Artery for the Differential Diagnosis of Thyrotoxicosis

AIM The differentiation of destruction-induced thyrotoxicosis and Graves' disease (GD) is of great importance for selection of proper therapy. Radioactive iodine uptake (RAIU) is the gold standard for differentiating these two conditions but its application has remained somewhat limited. Thyroid color Doppler flow sonography (CDFS) is a potential alternative of RAIU but more supporting evidence is warranted. In the present study, a standard operative procedure was developed to measure the mean peak systolic velocity of superior thyroid artery (STA-PSV) and evaluate its role in the differential diagnosis of thyrotoxicosis. METHODS A total of 135 patients with untreated thyrotoxicosis were enrolled into one retrospective study (GD, n = 103; thyroiditis, n = 32) and another prospective study recruited 169 patients (GD, n = 118; thyroiditis, n = 51). Thirty normal controls were also enrolled. Thyroid function, anti-TSH-receptor antibody (TRAb), RAIU, CFDS of thyroid and STA-PSV were performed for each patient. Receiver operator curve (ROC) was used to evaluate the diagnostic value of STA-PSV in a retrospective study so as to seek the optimal cutoff point. Then the cutoff point value was used to validate its diagnostic value in a prospective study and in another thyrotoxicosis population. RESULTS STA-PSV of GD was significantly higher than that of thyroiditis in both retrospective and prospective studies. The area under the ROC curve of mean STA-PSV was 0.8799 and 0.9447 in the retrospective and prospective studies respectively. If a mean STA-PSV cutoff point of 50.5 cm/s was set from the retrospective analysis for the prospective study, the sensitivity and specificity in distinguishing GD from thyroiditis were 81.04% and 96.08% respectively. Mean STA-PSV and TRAb had similar area under ROC. The coefficients of variation in STA-PSV measurement were lower than 10% for the euthyroid, thyroiditis and GD groups. CONCLUSIONS STA-PSV is a feasible supplement alternative of RAIU for differentiating the causes of thyrotoxicosis.