Validation and forensic application of a new 36 X-STR loci multiplex system

X-chromosomal short tandem repeats (X-STRs) are indispensable in specific cases, distinct from autosomal and Y chromosome genetic markers. SureID® X37 is an innovative six-color fluorescence multiplex detection system that can simultaneously amplify 36 X-STR loci (including DXS6795, DXS7132, DXS8378, DXS10101, DXS10103, DXS10079, DXS10134, GATA172D05, HPRTB, DXS6810, DXS10135, DXS6797, DXS10074, DXS7424, DXS9902, DXS7423, DXS10148, DXS10162, DXS6809, GATA31E08, DXS6803, DXS10075, DXS6807, DXS10164, DXS6789, DXS10146, DXS981, DXS9895, DXS101, DXS6800 DXS907, and DXS8377) and the Amelogenin locus. In this study, we validated its suitability for forensic identification per SWGDAM (Scientific Working Group on DNA analysis methods) guidelines, including PCR conditions, precision, accuracy, case-type samples, sensitivity, repeatability, reproducibility, species specificity, stability, stutter calculation, and DNA mixtures. Additionally, 577 Han Chinese individuals were used to investigate the utility of the system in forensic population genetics. The results indicated that the system is sensitive, stable, and reliable, and is suitable for typical forensic case. Subsequent population investigations confirmed that it serves as a potent supplementary tool in forensic applications.