Analytical validation of an RI sample cartridge with the RapidHIT® ID system

Evaluating the short tandem repeat (STR) in the field is important for the timely identification of a suspect. Several lines showed that the RapidHIT® ID system is reliable for DNA genotyping with buccal swabs and naked DNA. However, the application of this approach with blood samples has been poorly investigated. Because blood samples are among the most common forensic samples in our laboratory, further studies should be conducted. Here, we assessed the analytical performance of 19 STR loci with a newly developed RapidINTEL (RI) Sample Cartridge Kit by using the blood samples with known genotypes. Several commonly used substrates were included in the sensitivity study, and FTA cards proved to be the most promising sample carrier for blood storage and later identification. There was superior sensitivity and specificity with a 100% concordance rate for 0.5 μL of blood or 7 ng of genomic DNA. The performance for blood samples was comparable with that for the standard protocol. High success rate (90.57%) and high-concordance (100%) genotyping were automatically achieved over a wide range of operating conditions except for TH01. No contamination was observed throughout the study. Hematin, indigo, and humic acid had limited influence on the instrument system, while urea and melanin dramatically affected the genotyping results. Generally, the newly developed RI sample cartridge provided an alternative method for the STR genotyping of single-source blood samples over a wide range of operating conditions.