Improving the Accuracy of Papillary Thyroid Cancer Pathological Evaluation With Digital PCR Detection of the BRAF V600E Mutation

BACKGROUND: The BRAF V600E mutation is an important diagnostic factor for papillary thyroid cancer (PTC). Digital PCR (dPCR) is a relatively new technology featured with extremely high sensitivity. This study aims to evaluate the performance of dPCR in detecting BRAF V600E mutations in PTC diagnosis. METHODS: A total of 252 thyroid samples were collected in this retrospective diagnostic accuracy study. Diagnosis was made by a pathologist following histopathological guidelines. The BRAF V600E mutation was detected by dPCR and the results were compared with calls from amplification refractory mutation system PCR (ARMS-PCR) tests. Discrepant samples were evaluated again by two pathologists, and the presence of mutations was further confirmed by next generation sequencing (NGS). McNemar's test was used for paired categorical data in statistical analysis. RESULTS: Test results from dPCR and ARMS-PCR assays were in total agreement for PTC tumor and benign thyroid tissues. However, dPCR assays detected BRAF V600E mutations in four tumor-adjacent normal tissues, one lymph node sample, and two fine-needle aspirate (FNA) samples that were negative in ARMS-PCR tests, all with low frequencies of BRAF V600E mutations. When pathology results were used as the standard, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of dPCR assay were all 100% for tissue and FNA samples, while those of ARMS-PCR assay were 91.2%, 100%, 100%, 96.1%, and 92.9%, 100%, 100%, 95.7% for tissue and FNA samples, respectively. CONCLUSIONS: Our data demonstrate that dPCR is a highly valuable tool for PTC molecular pathology.