Prospective evaluation of thyroid imaging reporting and data system on 4550 nodules with and without elastography

Abstract

Objective: To evaluate prospectively the diagnostic accuracy of the thyroid imaging reporting and data system (TI-RADS) and its interobserver agreement and to estimate the reduction of indications of fineneedle aspiration biopsies (FNABs). Design: A prospective comparative study was designed. Methods: In 2 years, 4550 nodules in 3543 patients were prospectively scored using a flowchart and a six-point scale and then submitted to US-FNAB. Results were read according to the Bethesda system. Histopathological results were available for 263 cases after surgery. Sensitivity, specificity, negative predictive value (NPV) and positive predictive value, and accuracy were calculated for the gray-scale score, elastography, and a combination of both methods. Interobserver agreement was calculated using the kappa statistic. The reduction in the number of FNABs was estimated. Results: When compared with cytopathological results, sensitivity, specificity, NPV, and accuracy were 95.7, 61, 99.7, and 62% for the TI-RADS gray-scale score; 74.2, 91.1, 98, and 90% for elastography; and 98.5, 44.7, 99.8, and 48.3% for a combination of both methods respectively. When compared with histopathological results, the sensitivity of the gray-scale score, elastography, and a combination of both methods were 93.2, 41.9, and 96.7% respectively. Interobserver agreement for the six-point scale and the recommendation for biopsy were substantial (k valueZ0.72 and 0.76 respectively). The reduction in the number of FNABs was estimated to be 33.8%. Conclusion: The TI-RADS score has high sensitivity and NPV for the diagnosis of thyroid carcinoma. A hard nodule should always be considered as suspicious for malignancy but elastography cannot be used alone. Combination of elastography with gray-scale can be used to improve sensitivity or specificity. Interobserver agreement and decrease in unnecessary biopsies are significant.

Likelihood of malignancy in thyroid nodules according to a proposed Thyroid Imaging Reporting and Data System (TI-RADS) classification merging suspicious and benign ultrasound features

“…Later, Russ and cols. (12) validated their own proposed classification in 4550 nodules, which was further validated in other 242 nodules (17).…”

“…Since the size of microcalcifications has been reported to range from 0.5-3.0 mm in different studies (8-11,21;25,26,30), one should expect an overlap between micro-and macrocalcifications. However, macrocalcification as a possible suspicious feature has not been included in previous TI-RADS classifications (7,9,11,12,17). It is important to note that presence of macrocalcification is generally associated with an increased risk of malignancy (5,25,29).…”

“…All features positively and negatively associated with the likelihood of malignancy -which may be present in the same nodule -should be evaluated to yield an overall score. Previous authors have also evaluated the benign features of thyroid nodules (7,8,10,12,17). However, we attributed different weights to benign and malignant features, which resulted in a new and unique score, unlike the risk score for malignancy created by Kwak and cols.…”

“…However, this limitation has also plagued previous studies for ethical reasons (7)(8)(9)(10)(11)(12)17,18). In contrast, our subanalysis including only control thyroid nodules with a confirmed histopathology or a second FNAB strengthened our results.…”

“…Several authors (7)(8)(9)(10)(11)(12) have proposed different Thyroid Imaging Reporting and Data System (TI-RADS) classifications to standardize thyroid ultrasound reports, as demonstrated with the Breast Imaging Reporting and Data System (BI-RADS ® ) (13). Researchers have recently attempted to validate this type of approach as an instrument for use in clinical practice, with some authors proposing different TI-RADS versions in selected populations (14)(15)(16)(17)(18)(19)(20).…”