Electric Field–Induced Release and Measurement (EFIRM): Characterization and Technical Validation of a Novel Liquid Biopsy Platform in Plasma and Saliva

Electric field–induced release and measurement (EFIRM) is a novel, plate-based, liquid biopsy platform capable of detecting circulating tumor DNA containing EGFR mutations directly from saliva and plasma in both early- and late-stage patients with non–small-cell lung cancer. We investigated the properties of the target molecule for EFIRM and determined that the platform preferentially detects single-stranded DNA molecules. We then investigated the properties of the EFIRM assay and determined the linearity, linear range, precision, and limit of detection for six different EGFR variants (the four most common g.Exon19del variants), p.T790M, and p.L858R). The limit of detection was in single-digit copy number for the latter two mutations, and the limit of detection for Exon19del was 5000 copies. Following these investigations, technical validations were performed for four separate EFIRM liquid biopsy assays, qualitative and quantitative assays for both saliva and plasma. We conclude that EFIRM liquid biopsy is an assay platform that interrogates a biomarker not targeted by any other extant platform (namely, circulating single-stranded DNA molecules). The assay has acceptable performance characteristics in both quantitative and qualitative assays on both saliva and plasma.