Monitoring Outcomes of Indeterminate Thyroid Nodules and Predictive Capabilities of Molecular Testing.

Objective: This study aimed to compare the effectiveness of reflex molecular testing at identifying thyroid malignancy in indeterminate thyroid nodules (ITNs) since its implementation at our institution.

Method: Identified all ITNs at our institution from January 2010 to October 2020. Calculated the sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of ThyroSeq since the initiation of universal reflex testing of all first-time ITNs beginning in March 2016. Analyze effect on frequency of diagnostic surgeries.

Results: Study group: March 2016 to October 2020, 378 ITNs underwent ThyroSeq (318 Bethesda III and 60 Bethesda IV). Mean age 52 years, 35.9% male, 61.1% female. 145 surgically excised with overall resection rate of 38.4% (III: 32.7%; IV 68%). Final histology: 49 malignant with overall rate of malignancy (ROM) of ITNs at 33.8% (III: 31.7%; IV: 39%). ThyroSeq sensitivity for ITNs at 84% (III 78.8%, IV 93.8%). ThyroSeq NPV for ITNs at 86% (III 84%, IV 93.3%). ThyroSeq specificity for ITNs at 52% (III 50.7%, IV 56%). ThyroSeq PPV for ITNs at 47% (III 42.6%, IV 57.7%). Control group: From January 2010 to February 2016 there were 242 ITNs (152 Bethesda III, 90 Bethesda IV). Mean age 52.6 years, 25.8% male, 74.2% female. 157 cases were surgically excised, with an overall resection rate of 64.9% (III: 57.2%; IV: 77.8%). Final histology: 32 malignant, with overall ROM of ITNs at 20.4% (III: 27.6%; IV: 11.4%).

Conclusion: The initiation of universal Thyroseq (sensitivity 84% and NPV 86%) of ITNs at our institution has significantly decreased our percentage of diagnostic lobectomies, with a decreased resection rate of 26.5%.