[Comparison of the Forensic Testing Performance of Six STR Kits]

To compare the technical performance indicators of six commonly used STR kits, and to evaluate their capabilities in forensic testing.

The STR genotyping results of forensic DNA standard sample 9948 with different template quantities were analyzed using Identifiler^TM Plus, AGCU EX28CS, NHID^® 25A, Verifiler^TM Plus, VersaPlex^TM 27PY, and FastDirect^TM 25A. Differen-ces in detection sensitivity, allelic drop-out/in, allele peak height and heterozygote balance were eva-luated. Various PCR inhibitors, including humic acid, heme, indigo, calcium ions and ethylenediaminetetraacetic acid (EDTA), were added to the multiplex amplification systems to compare the maximum tolerance levels of the six kits to PCR inhibitors.

The detection sensitivity of Identifiler^TM Plus, AGCU EX28CS and VersaPlex^TM 27PY was as low as 100 pg, whereas the sensitivity of FastDirect^TM 25A, NHID^® 25A and Verifiler^TM Plus reached 50 pg. At different template quantities, the number of STR loci detected by the five kits was greater than that of Identifier^TM Plus. When detecting templates of 50 pg or less, the total number of allelic drop-out/in observed with the Identifiler^TM Plus was lower than that observed with the other five kits. The allele peak heights detected by AGCU EX28CS at 200 and 100 pg template quantities and by VersaPlex^TM 27 PY at 50 pg were significantly lower than those detected by Identifiler^TM Plus (P<0.05). Regarding resistance to inhibitors, NHID^® 25A showed stronger tolerance to humic acid (≤250 ng/μL), heme (≤0.6 mmol/L) and calcium ions (≤1.4 mmol/L) than other kits. It was found that VersaPlex^TM 27PY showed the strongest tolerance to indigo (≤0.048 mol/L); and FastDirect^TM 25A showed the strongest tolerance to EDTA (≤1.0 mmol/L). For heme, AGCU EX28CS and FastDirect^TM 25A showed lower tolerance than Identifiler^TM Plus, whereas the other three kits exhibited higher tolerance. For other inhibitors, all five kits demonstrated tolerance comparable to or higher than that of Identifiler^TM Plus.

Compared with Identifiler^TM Plus, AGCU EX28CS, FastDirect^TM 25A, NHID^® 25A, VersaPlex^TM 27PY and Verifiler^TM Plus show no obvious overall disadvantage in detection sensitivity, allelic drop-out/in, allele peak height, heterozygote balance and inhibitor resistance and even demonstrate superior performance in certain technical indicators.