One-step Nucleic Acid Amplification for Detection of Lymph Node Metastasis in Lung Cancer

Objective: Intraoperative diagnosis of lymph node (LN) metastasis is critical in lung cancer patients. The one-step nucleic acid amplification (OSNA) assay is a novel technique using a loop-mediated isothermal amplification method of gene amplification. The objective of this study was to investigate whether the OSNA assay provides sufficient diagnosis of LN metastasis in lung cancer patients.Methods: A total of 40 LN stations were dissected from the 20 patients, who had curative lobectomy for lung cancer. The cut halves of LNs were used for pathological diagnosis, and other halves were for the OSNA assay. The OSNA assay used cytokeratin (CK) 19 mRNA as a marker. The CK19 mRNA copy number was detected using RD-100i (Sysmex Corp., Hyogo, Japan). One formalin-fixed section with the largest cutting surface of the other halves of LNs was used for pathological examination. When discordance was observed between OSNA assay and usual pathological examination, an additional examination using 1-mm interval sections was performed.Results: In the forty LN stations, three stations were diagnosed as LN metastasis positive pathologically. In these three, the OSNA assays showed extremely high numbers of CK19 mRNA copies. When the cutoff value was set to 250 copies/μl, 4 stations with relatively low copy numbers were found to be discordant. Of the 4 discordant cases, one was shown to be micro-metastasis positive in the additional pathological assessment. The sensitivity of the OSNA assay was 100.0%, and its specificity was 91.7%.Conclusions: This method could be applied to intraoperative assessment LNs metastasis.