Zhao Shu-min, Zhang Su-hua, Li Cheng-tao
Shanghai Key Laboratory of Forensic Medicine, Institute of Forensic Science, Ministry of Justice, Shanghai 200063, PR China.
Fa Yi Xue Za Zhi. 2011 Apr;27(2):102-6.
To investigate the criterion for source identification of gastrointestinal tumor based on the number of identical allele (IAn) and the number of matched STR locus with 2 identical alleles (A2) in Identifiler system.
One hundred and five pairs of gastrointestinal tumor samples and homologous normal samples (TN group) were genotyped with Identifiler system. The numbers of STR locus with genotypic alteration (STRGA) in each tumor were determined by comparing the genotype of the matched STR loci in each pair of samples. According to the limited distribution of IAn and A2, 16 different values of IAn was substituted into the published discriminant functions to obtain the cut-off values of IAn and A2 for source identification of tumor sample. Indices including sensitivity (SEN), specificity (SPE), accuracy (AC), positive predictive value (PPV) and negative predictive value (NPV) for distinguishing tumor from an unrelated individual or a full sibling of the patient were calculated. Concordance of the identification results based on the determined criteria and the definite facts were statistically tested with Kappa index.
The total frequency of STRGA was 5.46%. There were 31.43% of the 105 tumor samples carried at least one STR locus with STRGA mutation. According to the Fisher discrimination rules, criteria I (IAn>or=23 and A2>or=8) and criteriall (IAn>or=26 and A2>or=11) meet the requirements of distinguishing tumor sample from an unrelated individual or a full sibling of the patient with tumor, respectively. SEN=0.971 0, PPV=1.000 0, PPV=0.891 9 and Kappa=0.923 5, when the criteria were used to determine the specified relatives.
Criteria I and criteria II were powerful for distinguishing tumor sample from an unrelated individual or a full sibling of the patient with tumor, respectively, when the Identifiler system was adopted for source identification of gastrointestinal tumor sample.
探讨基于Identifiler系统中相同等位基因数（IAn）及具有2个相同等位基因的匹配STR位点数量（A2）对胃肠道肿瘤进行来源鉴定的标准。
采用Identifiler系统对105对胃肠道肿瘤样本及其同源正常样本（TN组）进行基因分型。通过比较每对样本中匹配STR位点的基因型，确定每个肿瘤中发生基因型改变的STR位点数量（STRGA）。根据IAn和A2的有限分布，将16个不同的IAn值代入已发表的判别函数，以获得用于肿瘤样本来源鉴定的IAn和A2的截断值。计算用于区分肿瘤与无关个体或患者全同胞的敏感性（SEN）、特异性（SPE）、准确性（AC）、阳性预测值（PPV）和阴性预测值（NPV）等指标。采用Kappa指数对基于确定标准的鉴定结果与确定事实之间的一致性进行统计学检验。
STRGA的总频率为5.46%。105个肿瘤样本中有31.43%至少携带1个发生STRGA突变的STR位点。根据Fisher判别规则，标准I（IAn≥23且A2≥8）和标准II（IAn≥26且A2≥11）分别满足将肿瘤样本与无关个体或肿瘤患者的全同胞区分开来的要求。当使用这些标准来确定特定亲属时，SEN = 0.971 0，PPV = 1.000 0，NPV = 0.891 9，Kappa = 0.923 5。
在采用Identifiler系统对胃肠道肿瘤样本进行来源鉴定时，标准I和标准II分别能够有效地将肿瘤样本与无关个体或肿瘤患者的全同胞区分开来。
