Risk stratification of indeterminate thyroid nodules by novel multigene testing: a study of Asians with a high risk of malignancy

Molecular testing of indeterminate thyroid nodules informs about the presence of point mutations, insertions/deletions, copy number variants, RNA fusions, transcript alterations and miRNA expression. American Thyroid Association (ATA) guidelines suggest molecular testing of indeterminate thyroid nodules may be considered to supplement risk of malignancy (ROM). Although these recommendations have been incorporated in clinical practices in the United States, molecular testing of indeterminate thyroid nodules is not common practice in Asia. Here, we performed molecular testing of 140 indeterminate nodules from Chinese patients using a novel molecular platform composed of RNA and DNA‐RNA classifiers, which is similar to Afirma GEC and ThyroSeq v3. Compared with reports from North America, the new RNA and DNA‐RNA classifiers had a higher positive predictive value (p1 = 0.000 and p2 = 0.020) but a lower negative predictive value (p1 = 0.004 and p2 = 0.098), with no significant differences in sensitivity (p1 = 0.625 and p2 = 0.179) or specificity (p1 = 0.391 and p2 = 0.264). Out of 58 resected nodules, 10 were borderline and 33 malignant, indicating a 74.1% ROM, which was higher than reports in North America (10–40% ROM). Our findings emphasize molecular testing with the newly reported RNA and DNA‐RNA classifiers can be used as a ‘rule‐in’ test when ROM is high. About 20% of thyroid cytology findings are indeterminate, and molecular testing can be used for risk stratification. Here, we developed a novel molecular platform and performed molecular testing of indeterminate thyroid nodules. Our findings emphasize that molecular testing with the newly reported RNA and DNA‐RNA classifiers has a high positive predictive value and can be used as a ‘rule‐in’ test in Asia.