Zhao Shu-min, Zhang Su-hua, Li Cheng-tao
Shanghai Key Laboratory of Forensic Medicine, Institute of Forensic Science, Ministry of Justice, P.R. China, Shanghai 200063, China.
Fa Yi Xue Za Zhi. 2011 Feb;27(1):17-21.
To investigate the criteria of the number of identical allele (IAn) and the number of matched STR locus with 2 identical alleles (A2) for full sibling (FS) determination with Identifiler system.
According to the limited distribution of IAn. and A2, all of the 31 potential values of IAn. were substituted into the published discriminant functions to obtain the cut-off values of IAn and A2 for FS determination, and then 4 different criteria were determined to distinguish 280 FS pairs from 2283 individual pairs, respectively, which had been genotyped with Identifiler system. Cumulative full sibling index (CFSI) of the samples were calculated with ITO method, and 4 different criteria of CFSI (>1, > or =5, > or =20 and > or =100) were also utilized to determinate FS, respectively. Indices including sensitivity (SEN), specificity (SPE), accuracy(AC), positive predictive value(PPV) and negative predictive value (NPV) of the 8 different criteria for FS determination were calculated, respectively. Concordance of FS determination between the criteria based on IAn and A2 and that of CFSI were statistically tested with Kappa index.
All the individual pairs, which meet the requirement of (I) IAn > or =15 and A2 > or =4, or (II) IAn > or =16 and A2 > or =3, or (III) IAn > or = 17 and A2 > or =3, or (IV) IAn > or =18 and A2 > or =3, could been concluded as FS. AC, SPE and NPV of the 4 criteria mentioned above and the 4 criteria of CFSI were all over 0.9500 in FS determination. Indices between criterion II and CFSI > or =5, criterion III and CFSI > or =20, criterion IV and CFSI > or =100 were similar with each other and the Kappa indexes of the 3 groups were 0.9049, 0.9204 and 0.9083, respectively. PPV and NPV of criterion III and CFSI > or =20 were all over 0.9500.
The criterion of IAn > or =17 and A2 > or =3 was feasible and efficient for FS determination with Identifiler system, power of which was similar with the criterion of CFSI > or =20.
探讨运用Identifiler系统进行全同胞（FS）鉴定时，相同等位基因数（IAn）及具有2个相同等位基因的STR基因座匹配数（A2）的判定标准。
根据IAn和A2的有限分布情况，将IAn的31个可能值代入已发表的判别函数，得出用于FS鉴定的IAn和A2的截断值，进而确定4种不同标准，分别从2283对已用Identifiler系统进行基因分型的个体对中区分出280对FS。采用ITO法计算样本的累积全同胞指数（CFSI），并分别运用4种不同的CFSI标准（>1、≥5、≥20和≥100）来判定FS。分别计算8种不同FS判定标准的灵敏度（SEN）、特异度（SPE）、准确度（AC）、阳性预测值（PPV）和阴性预测值（NPV）。基于IAn和A2的标准与CFSI标准之间FS判定的一致性采用Kappa指数进行统计学检验。
所有满足以下条件之一的个体对可判定为FS：（I）IAn≥15且A2≥4；（II）IAn≥16且A2≥3；（III）IAn≥17且A2≥3；（IV）IAn≥18且A2≥3。上述4种标准以及4种CFSI标准在FS判定中的AC、SPE和NPV均超过0.9500。标准II与CFSI≥5、标准III与CFSI≥20、标准IV与CFSI≥l00之间的各项指标彼此相似，3组的Kappa指数分别为0.9049、0.9204和0.9083。标准III与CFSI≥20的PPV和NPV均超过0.9500。
IAn≥17且A2≥3的标准用于Identifiler系统进行FS鉴定是可行且有效的，其效能与CFSI≥20的标准相似。
