E.M. Henriksen2, E.A. Todd2, J. Chang2, E. Lopez2, C. Saghira1, A.C. Cioci1,2, T.M. Vaghaiwalla1,2, J.I. Lew1,2 1University Of Miami, DeWitt Daughtry Department Of Surgery, Division Of Endocrine Surgery, Miami, FL, USA 2University Of Miami, Leonard M. Miller School Of Medicine, Miami, FL, USA
Introduction:
The evaluation of thyroid nodules commonly includes fine needle aspiration (FNA) cytology for the diagnosis of papillary thyroid cancer (PTC). When FNA results reveal atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS), this cytology can be sent for next-generation sequencing (NGS). ThyroSeq V2.1 and Afirma are two widely available NGS tests, which use different sequencing techniques and diagnostic metrics. This study assesses the diagnostic accuracy of ThyroSeq V2.1 and Afirma to evaluate AUS/FLUS thyroid nodules.
Methods:
A retrospective study of prospectively collected data from 2525 patients who underwent NGS and thyroidectomy at a single institution between 2000 and 2022 was performed. Patients ≥18 years of age who had thyroid nodules with FNA results classified as AUS/FLUS (Bethesda III category) and underwent reflex NGS were included. Diagnostic metrics, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), false positive (FP) and false negative (FN) for both NGS tests were correlated to final histopathology of thyroid nodules with PTC.
Results:
A total of 339 patients with AUS/FLUS thyroid nodules underwent NGS testing, 47.5% (n=161) with Afirma and 52.5% (n=178) with ThyroSeqV2. For NGS tests overall, the sensitivity, specificity, PPV, NPV, FP and FN rates for PTC were 89.5%, 26.3%, 55.6%, 29.0%, 73.7% (n=123) and 10.5% (n=18). respectively. For Afirma, the sensitivity, specificity, PPV, NPV, FP and FN rates were 97.4%, 14.3%, 51.0%, 14.3% 85.7% (n=72) and 2.6% (n=2). For ThyroSeq V2.1, the sensitivity, specificity, PPV, NPV, FP and FN rates were 83.2%, 38.6%, 60.8%, 33.3%, 61.4% (n=51) and 16.8% (n=16), respectively.
Conclusion:
In this surgical series of patients with AUS/FLUS thyroid nodules, NGS tests were found to be equivocal. While Afirma testing has greater sensitivity, it has lower specificity and has a higher rate of FP. While ThyroSeq V2.1 testing has higher specificity, it also has a much higher rate of FN of 16.8%. Differences between NGS tests should be considered when interpreting results, and future studies examining preoperative factors in addition to NGS may be beneficial to stratify for thyroid malignancy.