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Anslinger, K.; Bayer, B.; Brune, V.; Schreier, I.; Tschoche, J.; Mariassy, D. von (2017): Laborinterne vs. vorgegebene Grenzwerte für die DNA-Typisierung. In: Rechtsmedizin, Vol. 27, No. 6: pp. 506-509
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Abstract

In routine case work stains with unknown DNA quantity and quality are first analyzed using quantitative PCR (qPCR). Based on these results the subsequent analysis can be optimized, and furthermore samples with insufficient DNA quantity or quality can be filtered out prior to short tandem repeat (STR) analysis. The appropriate thresholds are as a general rule determined by internal validation studies, which consider the complete laboratory set-up. Nevertheless, the performance requirements laid down in public invitations to tender increasingly contain obligatory default thresholds, which may differ from the laboratory-specific value. A study was initiated to verify if and to what extent potentially analyzable samples would be discarded if this regulation would be applied. A total of 2693 samples with DNA amounts between 0.5 pg/A mu l (laboratory-specific threshold corresponding to 5 pg total DNA amount per PCR set-up) and 5 pg/A mu l (default threshold, corresponding to 50 pg total DNA amount per PCR set-up) were analyzed. The profiles obtained were evaluated. It could be demonstrated that 36% of the samples (9% of single profiles suitable for storage in the German DNA database and 27% of mixtures suitable for comparison with reference samples) revealed usable DNA profiles, therefore, the use of generalized obligatory default thresholds does not seem to be useful.