In contrast with reports using KRAS plasmid DNA [10,21] to define assay sensitivity, this multiplex allele specific assay was standardized using human reference DNA from clinical samples or from tumor cell lines, permitting multiplex detection of at least 0.15% of mutant DNA (35 pg approximately, equivalent to 5 copies of mutant KRAS DNA) mixed with wild type genomic DNA. The gene discussed is KRAS; the disease is neoplasm.