(22.04) A Retrospective Analysis of Molecular Testing Regarding Cytologically Intermediate Bethesda III and IV Thyroid Nodule Biopsies: Experience at a Private Institution
Medical Assistant Endocrine Associates of West Village Flushing, New York, United States
Objective : The gold-standard diagnostic test for thyroid malignancy is fine-needle aspiration cytology (FNAC). While we can determine if the nodule is benign or malignant via FNAC, there are cases where the results are indeterminate, with a Bethesda III or IV score - suspicious for malignancy, atypia of undetermined significance, or follicular neoplasm. These biopsies are sent for genetic molecular testing, where they can be classified as suspicious or benign, and confirm whether genetic mutations are present. During molecular testing, a gene sequencing classifier amalgamates RNA expression of an assortment of genes. After testing, a shared-decision between provider and patient regarding course of treatment is made. If surgery is necessary, the surgical pathology report will concretely confirm whether malignancy is present. Our objective is to compare our smaller institution's data with studies from larger populations to illustrate efficacy of these tests throughout varying populations. This would solidify that using molecular testing can aid in ruling out malignancy in thyroid nodules and prevent overtreatment.
Methods: A retrospective chart review was completed on all patients who underwent thyroid FNAC in our institution. Subsequent molecular testing from the gene sequencing classifier was analyzed and compared with surgical pathology reports as a gold-standard. Statistical analysis was used in the comparison in order to generate positive predictive values (PPV), negative predictive values (NPV), sensitivity, and specificity.
Results: A total of 1088 thyroid FNACs have been performed in our private institution in a span of 12 years - utilizing a specific lab for cytology and molecular testing. 75% of the total population (n = 813/1088) yielded benign results, 3% (n= 32/1088) yielded malignant results, and 12% (n = 135/1088) yielded indeterminate results. Statistical analysis of our numbers was conducted and we deduced a PPV of 0.57, and a high sensitivity (0.93), specificity (0.98), and NPV (1.0).
Discussion/Conclusion: Based on our analysis, we determined that our specific lab can rule in malignancy 98% of the time if a subject tests positive for malignancy and can rule out malignancy 93% of the time if a subject tests negative for malignancy. With a PPV of 57%, the lab delineates moderate precision in terms of detecting true positives. With a NPV of 100%, the lab delineates high assurance that a negative test means no presence of malignancy. The values from our statistical analysis are comparable to the larger population, illustrating that molecular testing is an effective way to rule out thyroid carcinoma in individuals from varying populations.
