Single nucleotide polymorphism profiling assay to exclude serum sample mix-up.

Sample mix-ups are a threat to the validity of clinical laboratory test results. To detect serum sample mix-ups we developed a single nucleotide polymorphism (SNP) profiling test. SNPs are frequent sequence variations in the human genome. Each individual has a unique combination of these nucleotide variations. Predeveloped SNP amplification assays are commercially available. We recently discovered that these SNP assays could be applied to serological samples, which is not self-evident because a key step in serum preparation is removal of white blood cells, the major source of DNA, from blood. DNA was extracted from serum samples. Real-time polymerase chain reaction (PCR) analysis of the purified DNA using a selection of 10 SNP assays provided SNP profiles. The applicability of the SNP profiling test was demonstrated by means of a case where hepatitis E virus serological determinations of four serum samples of one patient seemed inconsistent. SNP profiling of the samples demonstrated that this was due to the enzyme-linked immunosorbent assay test instead of sample mix-up. We have developed an SNP profiling assay that provides a way to link human serum samples to a source, without post-PCR processing. The chance for two randomly chosen individuals to have an identical profile is 1 in 18 000. Solving potential serum sample mix-ups will secure downstream evaluations and critical decisions concerning the patients involved.