RFLP band size standards: cell line K562 values from 1991 to 1997 proficiency studies

Cell line K562 is the defacto forensic control material for forensic restriction fragment length polymorphism (RFLP) DNA profiling in the U.S. Fifty-one proficiency tests conducted from 1991 through 1997 enable a detailed description of RFLP measurement performance during this period. Sufficient data are available to define reference distributions for all commonly utilized and many less commonly reported genetic loci, for both HaeIII- and HinfI-based RFLP systems. The average measured size of HaeIII locus D1S7 and D5S110 bands has varied slightly over time; while relatively small, these temporal changes add to the overall interlaboratory measurement uncertainty. The characteristic standard deviation for HinfI RFLP system measurements has a nearly identical dependence on expected band size as does the standard deviation for HaeIII measurements. The ellipsoidal distance, K, is suggested for use as an RFLP data quality metric; the critical threshold value that on average excludes 1% of plausibly valid proficiency data for a given polymorphic locus is K1% = 14.2.