Precision and accuracy in fluorescent short tandem repeat DNA typing: assessment of benefits imparted by the use of allelic ladders with the AmpF/STR Profiler Plus kit.

Base-calling precision of short tandem repeat (STR) allelic bands on dynamic slab-gel electrophoresis systems was evaluated. Data was collected from over 6000 population database allele peaks generated from 468 population database samples amplified with the AmpF/STR Profiler Plus (PP) kit and electrophoresed on ABD 377 DNA sequencers. Precision was measured by way of standard deviations and was shown to be essentially the same, whether using fixed or floating bin genotyping. However, the allelic ladders have proven more sensitive to electrophoretic variations than database samples, which have caused some floating bins of D18S51 to shift on occasion. This observation prompted the investigation of polyacrylamide gel formulations in order to stabilize allelic ladder migration. The results demonstrate that, although alleles comprised in allelic ladders and questioned samples run on the same gel should migrate in an identical manner, this premise needs to be verified for any given electrophoresis platform and gel formulation. We show that the compilation of base-calling data is a very informative and useful tool for assessing the performance stability of dynamic gel electrophoresis systems, stability on which depends genotyping result quality.