Screening Biological Stains with qPCR versus Lateral Flow Immunochromatographic Test Strips: A Quantitative Comparison using Analytical Figures of Merit

Biological fluid identification is an important facet of evidence examination in forensic laboratories worldwide. While identifying bodily fluids may provide insight into which downstream DNA methods to employ, these screening techniques consume a vital portion of the available evidence, are usually qualitative, and rely on visual interpretation. In contrast, qPCR yields information regarding the amount and proportion of amplifiable genetic material. In this study, dilution series of either semen or male saliva were prepared in either buffer or female blood. The samples were subjected to both lateral flow immunochromatographic test strips and qPCR analysis. Analytical figures of merit—including sensitivity, minimum distinguishable signal (MDS) and limit of detection (LOD)—were calculated and compared between methods. By applying the theory of the propagation of random errors, LODs were determined to be 0.05 μL of saliva for the RSID™ Saliva cards, 0.03 μL of saliva for Quantifiler® Duo, and 0.001 μL of semen for Quantifiler® Duo. In conclusion, quantitative PCR was deemed a viable and effective screening method for subsequent DNA profiling due to its stability in different matrices, sensitivity, and low limits of detection.