Validation of the AGCU Expressmarker 20 + 20Y kit: A 6-dye multiplex assay for forensic application

The AGCU Expressmarker 20 + 20Y Kit is a newly devised short tandem repeat (STR) multiplex system that simultaneously analyses a set of 19 autosomal STR loci, 20 Y chromosomal STR loci and the amelogenin locus with six-dye fluorescent labelling. Here, the AGCU Expressmarker 20 + 20Y system was validated following the guidelines published by the Scientific Working Group on DNA Analysis Methods (SWGDAM), including PCR-condition, sensitivity, mixtures, species specificity, models of inhibition, precision, stutter percentage, concordance, population genetic studies, performance on three kinds of degraded DNA and a type of casework samples. The results indicated that the kit had high sensitivity when there was a small amount of DNA (0.0625 ng), more than one male (minor: major=1:19), or a mixture of males and females (male: female=1:32), models of inhibition (250 μM hematin, 1500 ng/μL humic acid and more than 100 ng/μL tannic acid) and degraded samples. The kit showed high precision level with standard deviation of allele size no more than 0.0930. Furthermore, this system was also tested in 444 random male samples of Chinese Han and Hui population, showing its high discrimination capability in Han and Hui population. Meanwhile, the system was applicable to the case of the AMELY abnormality. In short, the kit was verified and proved to be a robust, reliable and suitable tool for human identification and casework samples.