To compare diagnostic values of the 2015 American Thyroid Association (ATA) Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer with the thyroid imaging reporting and data system (TI-RADS) for sonographic malignancy risk stratification of thyroid nodules.

From November 2011 to December 2015, 485 thyroid nodules in 331 patients (mean age, 42.9 years±10.4)were included in this study. Characteristics includingsize, composition, shape(nonparallel or parallel), margin, echogenicity, calcifications and extrathyroidal extension of thyroid nodules were evaluated. Every nodule was stratificated by criteria set by TI-RADS and ATA guidelines, and malignant rate of each risk stratification were calculated and analysed. With pathology as the gold standard, different cutoff were taken to diagnose malignant nodules, and the sensitivity, specifity, positive predictive value, negativepredictive value and accuracy of the two methodologies were calculated at each cutoff. And the two methodologies were evaluated and measured by ROC curve.Finally their Kappa value were calculated at the best cutoff.

Of the 485 thyroid nodules, 96 were benign and 389 were malignant. The malignancy rates under TI-RADS category 2, 3, 4a, 4b, 4c, and 5 nodules were 0, 12.0% (3/25), 22.2% (10/45), 29.8% (14/47), 99.2% (261/363) and 100% (101/101). Malignancy rates under ATA guidelines of benign, very low, low, intermediate, and high suspicion for malignancy were 0,12.5% (1/8), 16.1% (10/62), 27.7% (13/47), and 99.2% (365/368). There were significant differences inside each patterns (P<0.01) respectively and high correlation between risk stratification with TI-RADS (r=0.70) and ATA guidelines (r=0.83). Areas under the ROC curve of the TI-RADS and ATA guidelines classifications were 0.966 and 0.959. Best cut-off point for diagnosing malignant by TI-RADS and ATA guideline classifications were ≥4c and ≥high suspicion, and at that point, diagnostic value of TI-RADS and ATA guidelines were nearly the same(sensitivity, 93.1% vs 93.8%; specificity, 97.9% vs 96.9%; PPV, 99.5% vs 99.2%; NPV, 75.7%vs 79.5%; and accuracy, 94.0%vs 94.4%), and there was no significant differences (P=0.50, P=0.50, P=0.50, P=0.53, P=0.55), Kappa=0.97.

Both TI-RADS and the ATA guidelinesprovide effective malignancy risk stratification for thyroid nodules. The diagnosticvalue of TI-RADS when considering≥4c and ATA guidelines when considering ≥high-suspicion nodules as malignant were nearly the same and both high.