S100B protein concentrations in cord blood: correlations with gestational age in term and preterm deliveries.

individuals 4, 5, and 6 were HbA/S heterozygotes and homozygous for non-E; individuals 7, 8, and 9 were homozygous for both HbS and non-E; and individuals 10, 11, and 12 were HbA homozygotes and non-E/HbE heterozygotes. These data also demonstrate an additional advantage of this multiplexed fluorescent bead arraybased approach. Because it is very rare for an individual to be negative for all four of the b-globin alleles being assessed in this study, the majority of samples will yield positive background-subtracted MFIs for at least one b-globin allele, which will also serve as an internal positive control. Those samples negative for all of the alleles being assessed would most likely represent PCR failures and require retesting. The interexperimental variation for this genotyping methodology was also assessed. As shown in Table 1, the standard deviations calculated from the background-subtracted MFIs from the three experiments did not interfere with the ability to correctly designate the b-globin genotype of these individuals. These data suggest that the results from each experiment are correct and that the retesting rate should be low. In conclusion, we have shown that this multiplexed fluorescent bead array-based genotyping methodology can be used to accurately determine the allelic composition at two b-globin loci, using dried blood spots from newborns. The array of fluorescent beads is flexible and could be expanded to include additional b-globin mutations or other clinically important genetic loci. This method would also be adaptable to automation to meet the high throughput requirements of a large newborn screening program.