LBODP107 Real World Performance Of The Afirma Xpression Atlas In Bethesda III And IV Thyroid Nodules. A Private Practice Experience

Fine Needle Aspiration (FNA) has modified all methods for diagnosing thyroid cancer; and in conjunction with the Bethesda System and the genomic sequencing classifiers (GSC), clinicians can objectively identify the risk of malignancy of thyroid nodules prior to surgical interventions. To further characterize these thyroid nodules, the Afirma Xpression Atlas (XA), a form of The Cancer Genome Atlas, was created and launched in May 2018. In November 2019 and March 2020, the Afirma XA panel was expanded to include 905 genomic variants and 235 fusions from 593 genes. Post-validations studies for the Afirma XA have been developed in well recognized large academic centers with unclear applicability or extrapolation to small endocrinology centers, which may have a different patient's population and thyroid cancer prevalence. This study was designed to analyze and objectively measure the performance of the Afirma XA in Bethesda III and IV thyroid nodules classified as GSC suspicious in our private endocrinology practice. We conducted a retrospective cohort analysis comparing all indeterminate and GCS suspicious nodules with their respective final surgical pathology results between June 2018 to October 2021. Forty-two thyroid nodules were studied, and the Bethesda III category was the predominant cytopathology discovered, representing 69% of all indeterminate nodules. Afirma XA was able to identify genomic alterations in only 40% of all included nodules. We found a 35% (CI: 15%-59%) sensitivity, 54% (CI: 32%-75%) specificity, 47% (CI: 35%-59%) of negative predictive value, and 41% (CI: 25%-60%) of positive predictive value when a 47% of cancer prevalence is applied. Based on this data, we conclude that Afirma XA cannot be used exclusively as a rule-out or a ruled-in test in GSC suspicious, Bethesda category III and IV thyroid nodules in small private endocrinology practices. Presentation: No date and time listed