Ultrasound grayscale ratio: a reliable parameter for differentiating papillary thyroid microcarcinoma from micronodular goiter

Abstract Background: To evaluate the reliability and diagnostic efficacy of the ultrasound grayscale ratio (UGSR) for differentiating papillary thyroid microcarcinomas (PTMC) from micronodular goiters (diameter ≤ 1.0cm).Methods: The ultrasound data of 241 pathologically-confirmed cases of patients with 265 PTMC and 141 patients with 168 micronodular goiters were retrospectively reviewed. All patients underwent outpatient ultrasonic examination and preoperative ultrasonic positioning. The RADinfo radiograph reading system (Zhejiang RAD Information Technology Co., Ltd., China) was used to measure and calculated the UGSR of PTMC, micronodular goiters. Patients were divided into the outpatient examination, preoperative positioning, and mean value groups, and the receiver operating characteristic curves (ROC) were calculated to obtain the optimal UGSR threshold for distinguishing PTMC from micronodular goiters.Results: The UGSR values of the PTMC and micronodular goiters were 0.56±0.14 and 0.80±0.19 (t=5.84, P<0.01) in the outpatient examination group, 0.55±0.14 and 0.80±0.19 (t=18.74, P<0.01) in the preoperative positioning group, and 0.56±0.12 and 0.80±0.18 (t=16.49, P<0.01) in the mean value group. The areas under the ROC curves in the outpatient examination, preoperative positioning, and mean value groups were 0.860, 0.856, and 0.875, respectively. When the cut-off UGSR values for the outpatient examination, preoperative positioning, and mean value groups were 0.649, 0.646, and 0.657, the sensitivity and specificity for predicting PTMC were 78.9% and 86.9%, 79.2% and 83.9%, 82.6%, and 85.7%, respectively. A reliable UGSR value was obtained between the outpatient examination and preoperative positioning groups (ICC=0.79, P=0.68).Conclusion: The UGSR is an accurate and feasible tool for differentiating PTMC from micronodular goiters with better diagnostic efficacy.