The level of somatic mutations in a tumor, called tumor mutational burden (TMB), is used as a biomarker to predict patient response to immune checkpoint inhibitor therapy, with cancer type-specific TMB cut-offs of clinical value. Whole exome sequencing (WES) has been the gold standard to measure TMB. While targeted panels have the capacity to estimate TMB, TMB scores can vary significantly depending on the panel size, coverage regions, and bioinformatics pipeline used to make variant calls. LGC SeraCare has developed Seraseq gDNA TMB Reference Panel Mix, which has been extensively validated using WES and can be used to guide TMB score assessment using targeted panels, especially around values that may be clinical decision points for different tumor types. Each Seraseq gDNA TMB Reference Panel Mix contains five vials of purified genomic DNA from tumor-like human cell lines encompassing complex genomic signatures over a broad range of TMB scores, all in one kit.