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

Background and Objectives  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. Materials and Methods  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. Results  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. Conclusion  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.