Rapid identification of blood using RT-RPA: A pilot study

This study details the detection of blood remote from a laboratory using a direct recombinase polymerase amplification reaction integrated with a lateral flow assay. The assay targets the ALAS 2 gene; a marker used in mRNA assays for the identification of blood in body fluid assignments. The process can be used at scenes as no specialized equipment is needed; the assay is efficient between 17°C and at least at 45°C. A result can be obtained in 10 min if the ambient temperature is more than 25°C but this time increases to 40 min if cooler than 25°C. Like any test for a body fluid, the assay needs to be highly sensitive, positive results were obtained with this assay from blood dilute to 0.0005 μL. The test was found to be specific for blood as positive results were only recorded in the presence of blood and no other body fluid. The reagents as a solution were stable for 3 days at 4°C adding to their potential use outside of laboratory conditions. The assay is straightforward to perform yielding results that can be interpreted easily. While not replacing presumptive tests, this can be used to further give confidence in assigning a sample as blood.