False homozygosities at various loci revealed by discrepancies between commercial kits: implications for genetic databases

Routine control of 2055 consecutive genotypes revealed discrepancies between the profiles established with the SGM plus and/or Profiler plus kits on one hand, and the profiles established with the Powerplex16 kit on the other hand. Furthermore, five discrepancies for vWA, three for D8S1179, two for FGA and three for D18S51 loci were found. In 10 cases (loci vWA, FGA, D18S51, D8S1179), the SGM plus and/or Profiler plus profiles showed homozygosity and the Powerplex16 genotype revealed heterozygosities which were confirmed to be true, both by typing with individual primer pairs and DNA sequencing. In four cases (two discrepancies at locus FGA, one at D18S51 and an abnormal paternity pattern for D5S818), the Powerplex16 kit showed apparent homozygosity and the SGM plus and/or Profiler plus kits showed heterozygosity. Mutation analysis could be performed for some of these individuals and evidenced variants, presumably leading to an annealing failure of one primer; the identified mutations are reported. It is suggested that databases should include information about the kits used to determine the profiles while ensuring that the primer sequences are made available.