## 4 Discussion
Using this assessment criterion, there was a substantial improvement in specificity with a moderate decrease in sensitivity leading to a significant improvement in the overall accuracy. Using the samples of the present study, the overall diagnostic accuracy was improved from 58.5% to 80.2% in \(E_{\text{maximum}}\) and to 78.3% in \(E_{\text{mean}}\). Although the diagnostic accuracy of combining GSU and SWE in our study was similar to those in previous studies, our study demonstrated substantial improvement in in the diagnostic accuracy after combining the two techniques, whereas previous studies showed no significance difference or decreased in the diagnostic accuracy [34; 36; 39; 40] (Table 4). The similar accuracy of the present study (78.3-80.2%) and previous studies (60.3-87.2%) was probably due to the use of different samples of the patients in the studies. However, we believe that the method that we proposed in our study can enhance the diagnostic accuracy in differential diagnosis of thyroid nodules. In routine clinical thyroid ultrasound examination, operators should consider examining the internal cervical chain to identify any metastatic cervical lymph nodes when malignant thyroid nodule is found. Ultrasound is a useful imaging tool to assess cervical lymph nodes. Metastatic cervical lymph nodes from papillary thyroid carcinoma are usually hyperechoic when compared to adjacent muscles, round in shape, without echogenic hilus, and have punctate calcification [41]. In addition, the combination of ultrasound and computed tomography can help to predict extrathyroid extension [42], and fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scans should be considered for detecting metastases in post-operative patients with aggressive histology of differentiated thyroid cancer [43]. In the present study, there were 84 benign and 27 malignant thyroid nodules. The calculated power of this sample size in evaluating the performance of GSU and SWE indices in distinguishing benign and malignant thyroid nodules ranged between 0.874 and 0.999 (G*Power version 3.1.9.2, Dusseldorf, Germany). There were limitations in the present study. The majority of the malignant thyroid nodules were papillary thyroid cancer, and thus we did not evaluate the difference of SWE indices among different types of malignant thyroid nodules. Future studies with larger sample size of various types of thyroid cancer can be conducted to investigate the value of SWE in differential diagnosis of different types of thyroid cancer. We did not evaluate the intra-operator and inter-operator reliability in SWE measurement of thyroid nodule stiffness. However, a previous study reported that SWE has satisfactory intra-operator (0.65-0.78) and inter-operator (0.72-0.77) reliability in the evaluation of neck lesions [35]. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Studies Involved and SWE Index Used**} & \multicolumn{2}{c}{**Diagnostic Accuracy (\%)**} & \multirow{2}{*}{**Difference in Diagnostic Accuracy (\%)**} \\ \cline{2-3} \cline{5-5}  & **GSU Alone** & & **GSU + SWE** \\ \hline Present study & & & \\ \(E_{\text{maximum}}\) (67.3 kPa) & \(58.5\) & \(80.2\) & \(21.7\) \\ \(E_{\text{mean}}\) (23.1 kPa) & \(58.5\) & \(78.3\) & \(19.8\) \\ \hline [PERSON] et al. [36] & & & \\ \(E_{\text{maximum}}\) (65 kPa) & \(81\) & \(77.9\) & \(-3.1\) \\ \hline [PERSON] et al. [34] & & & \\ \(E_{\text{minimum}}\) (85.2 kPa) & \(86.3\) & \(87.2\) & \(0.9\) \\ \hline [PERSON] et al. [39] & & & \\ \(E_{\text{minimum}}\) (39.3 kPa) & \(60.3\) & \(60.3\) & \(0\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Differences in diagnostic accuracy between the results of the present and previous studies to highlight the significant improvement achieved in the current study.