Theory and methodology for utilizing genes as biomarkers to determine potential biological mixtures

PURPOSE: Genetically determined Mixture information can be used as a surrogate for physical or behavioral characteristics in epidemiological studies examining research questions related to socially stigmatized behaviors and horizontally transmitted infections. A new measure, the probability of mixture discrimination (P-MD), was developed to aid mixture analysis that estimates the ability to differentiate single from multiple genomes in biological mixtures.METHODS: Four autosomal short tandem repeats (STRs) were identified, genotyped and evaluated in African American, European American, Hispanic, and Chinese individuals to estimate PMD. Theoretical P-MD frameworks were also developed for autosomal and sex-linked (X and Y) STR markers in potential male/male, male/female and female/female Mixtures.RESULTS: Autosomal STRs genetically determine the presence of multiple genomes in mixture samples Of unknown genders with more power than the apparently simpler X and Y chromosome STRs. Evaluation of four autosomal STR loci enables the detection of mixtures of DNA from multiple sources with above 99% probability in 211 four racial/ethnic populations.CONCLUSIONS: The genetic-based approach has applications in epidemiology that provide viable alternatives to survey-based study designs. The analysis of genes as biomarkers can be used as a gold standard for validating measurements front self-reported behaviors that tend to be sensitive or socially stigmatizing, such as those involving sex and drugs

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