Quality Control

Abstract

Quality control (QC) is one aspect of quality assurance (QA). Quality assurance also includes (1) periodic laboratory audits by external specialists, (2) keeping upto-date clearly-written protocols, (3) preparation of QA reports, (4) troubleshooting, (5) equipment maintenance and calibration, (6) methodology development, (7) personnel training, (8) continuing education, and (9) laboratory safety. To be assured of ongoing quality performance, laboratory accreditation is mandatory. The above aspects have been discussed throughout this text; however, because DMA profiling often involves legal considerations, details of QC are presented in this chapter. An extremely important report, Guidelines for a Quality Assurance Program for DNA Restriction Fragment Length Polymorphism Analysis, prepared by the Quality Assurance Subcommittee of TWGDAM, is included in Appendix I (Mudd 1989). Quality control, narrowly defined, is directly concerned with the accuracy and precision of laboratory results for specimens of verified origin. Implicit in this definition is assurance that correct and accurate population allele frequencies are used in probability calculations. The expert witness representing the laboratory must ensure that (1) the correct specimen is analyzed, (2) the DNA is not significantly degraded, (3) the specimens are not significantly contaminated with extraneous DNA, (4) the analysis procedure is well-controlled, (5) result interpretation is correct, and (6) no deviations from the authorized laboratory protocol have occurred. The expert witness in DNA profiling should be a meticulous analyst with a solid grasp of genetic and biochemical principles combined with considerable experience in recombinant DNA processes. A reasonable understanding of the concepts and application of statistical techniques, especially probability, is a definite asset. The ability to articulate the results of an analysis and to respond under cross examination to in-depth questions concerning principles, techniques, and chain of custody is mandatory. (See Wetli 1989 for a general overview on appearing as an expert witness.) A set of objective QC criteria must be established and followed to ensure that neither false negative nor false positive DNA profile match results are released from a service laboratory.