title: Evaluation of parameters in mixed male DNA profiles for the Identifiler® multiplex system.
abstract: The analysis of complex DNA mixtures is challenging for forensic DNA testing. Accurate and sensitive methods for profiling these samples are urgently required. In this study, we developed 11 groups of mixed male DNA samples (n=297) with scientific validation of D‑value [>95% of D‑values ≤0.1 with average peak height (APH) of the active alleles ≤2,500 rfu]. A strong linear correlation was detected between the peak height (PH) and peak area (PA) in the curve fit using the least squares method (P<2e-16). The Kruskal-Wallis rank-sum test revealed significant differences in the heterozygote balance ratio (H(b)) at 16 short tandem repeat (STR) loci (P=0.0063) and 9 mixed gradients (P=0.02257). Locally weighted regression fitting of APH and Hb (inflection point at APH = 1,250 rfu) showed 92.74% of H(b) >0.6 with the APH ≥1,250. The variation of H(b) distribution in the different STR loci suggested the different forensic efficiencies of these loci. Allelic drop-out (ADO) correlated with the APH and mixed gradient. All ADOs had an APH of <1,000 rfu, and the number of ADO increased when the APH of mixed DNA profiles gradually decreased. These results strongly suggest that calibration parameters should be introduced to correct the deviation in the APH at each STR locus during the analysis of mixed DNA samples.
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, Shijiazhuang, Hebei 050017, P.R. China.
authors.forename: Na
authors.initials: N
authors.lastname: Hu
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, Shijiazhuang, Hebei 050017, P.R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Cong
authors.affiliation: Institute of Statistics, Renmin University of China, Beijing 100872, P.R. China.
authors.forename: Tao
authors.initials: T
authors.lastname: Gao
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, Shijiazhuang, Hebei 050017, P.R. China.
authors.forename: Rong
authors.initials: R
authors.lastname: Hu
authors.affiliation: Institute of Statistics, Renmin University of China, Beijing 100872, P.R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.affiliation: DNA Laboratory, Forensic Science Service of Beijing Public Security Bureau, Beijing 100085, P.R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Tang
authors.affiliation: DNA Laboratory, Forensic Science Service of Beijing Public Security Bureau, Beijing 100085, P.R. China.
authors.forename: Luyan
authors.initials: L
authors.lastname: Xue
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, Shijiazhuang, Hebei 050017, P.R. China.
authors.forename: Shujin
authors.initials: S
authors.lastname: Li
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, Shijiazhuang, Hebei 050017, P.R. China.
authors.forename: Chunling
authors.initials: C
authors.lastname: Ma
mesh_terms: D000483:Alleles; D002138:Calibration; D004247:DNA / Q000032:analysis*; D053803:Forensic Genetics / Q000379:methods*; D056426:Genetic Loci; D006579:Heterozygote; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D018895:Microsatellite Repeats; D060885:Multiplex Polymerase Chain Reaction / Q000379:methods* / Q000592:standards
chemical_list: D004247:DNA