Evaluation of real-time PCR results at the limit of detection

Real-time polymerase chain reaction (realtime PCR) facilitates to detect DNA fragments at very low copy numbers. Positive results, e.g. for unauthorized genetically modified organism (GMO)contamination or for allergens, may raise safety concerns and have far-reaching consequences. However, in case of very low concentrations of DNA samples, results for the same product lot or even for identical samples from different laboratories may differ. Therefore, an approach for a standardized interpretation and reporting of results obtained by real-time PCR at the limit of detection (LOD) is proposed.A quality control DNA sample containing the target at the LOD (95 %) is analysed in parallel withthe real DNA sample and the respective CT values are compared. In addition, practical approaches for in house and precision-based estimation of the LOD are presented. The proposed approach may also contribute to the current discussion on implementing a technical solution to handle DNA traces in specimen, e.g. for the detection of unauthorized GMO.