Interlaboratory comparison of autoradiographic DNA profiling measurements: precision and concordance

Knowledge of the expected uncertainty in restriction fragment length polymorphism (RFLP) measurements is required for confident exchange of such data among different laboratories. The total measurement uncertainty among all Technical Working Group for DNA Analysis Methods laboratories has previously been characterized and found to be acceptably small. Casework cell line control measurements provided by six Royal Canadian Mounted Police (RCMP) and 30 U.S. commercial, local, state, and Federal forensic laboratories enable quantitative determination of the within-laboratory precision and among-laboratory concordance components of measurement uncertainty typical of both sets of laboratories. Measurement precision is the same in the two countries for DNA fragments of size 1000 base pairs (bp) to 10,000 bp. However, the measurement concordance among the RCMP laboratories is clearly superior to that within the U.S. forensic community. This result is attributable to the use of a single analytical protocol in all RCMP laboratories. Concordance among U.S. laboratories cannot be improved through simple mathematical adjustments. Community-wide efforts focused on improved concordance may be the most efficient mechanism for further reduction of among-laboratory RFLP measurement uncertainty, should the resources required to fully evaluate potential cross-jurisdictional matches become burdensome as the number of RFLP profiles on record increases.