Abstract
Aim. Several amplification and detection formats for the analysis of short tandem repeat loci are readily available to the forensic laboratory. Careful consideration must be given to the throughput, sensitivity, concordance, data interpretation, facility requirements, and costs of operation. The Pennsylvania State Police DNA Laboratory sought to establish that of any of the amplification or detection formats generally used in the United States generates concordant results and that the use of several formats within one laboratory provides a solution to the interpretation of difficult evidentiary samples.
Methods. Validation work consisting of sensitivity, precision, mixture, and substrate studies was performed by use of each of three detection formats (ABI Prism((R))310 Genetic Analyzer, ABI Prism((R))377 DNA Sequencer, and the Hitachi (FMBIOII)-I-(R) Fluorescent Scanner) and three amplification systems (GenePrint((R)) PowerPlex (TM) 16, GenePrint((R)) PowerPlex (TM) 1.1/2.1, and Ampf/STR (TM) Profiler Plus/COfiler). The results generated in each of the formats were compared, along with the problems incurred.
Results. All allele calls were concordant, with the exception of primer region variants, and all detection systems were sensitive and reliable. Even with the use of multiple formats, a general protocol can be written with only one set of interpretation guidelines.
Conclusion. National databases can be used with input data from any of these formats. The use of several detection formats al towed the forensic scientist to select a system, based on sample quality, quantity, and throughput requirements. Interpretation issues resulting from complex mixtures, degraded samples, rare microvariants, internal primer variants, unusual heterozygote ratios, above or below ladder alleles, and potential tri-alleles can be verified.