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Considerations for the interpretation of STR results in cases of questioned half‐sibship
Author(s) -
Allen Robert W.,
Fu Jun,
Reid Thomas M.,
Baird Michael
Publication year - 2007
Publication title -
transfusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.045
H-Index - 132
eISSN - 1537-2995
pISSN - 0041-1132
DOI - 10.1111/j.1537-2995.2006.01144.x
Subject(s) - statistics , mathematics
Likelihood ratios (LRs) were calculated for a cohort of 60 pairs of true half‐sibs and compared with LR values calculated for unrelated, paired children. STR results for the half‐sib group were obtained from 60 archived cases involving a true mother, two children, and an alleged father subjected to typing with a multiplex STR kit (Identifiler multiplex, Applied Biosystems) and in which the alleged father was excluded as the father of only one of the two children (half‐sib pairs). The distribution of LR values among true half‐sibs was compared to those produced from paired, unrelated children selected in two ways: One method for producing unrelated pairs was to randomly select Identifiler profiles from children in 120 distinct paternity cases and group them into 60 ethnically matched pairs (random pairs). In a second approach, the children in the true half‐sib group were shuffled and ultimately paired with someone from a different case. A total of 49 ethnically matched, unrelated pairs were created (shuffled pairs). In the shuffled pairs group, comparisons were thus based on a constant set of phenotypes. LRs comparing the probability of half‐sibship versus being unrelated were produced for all groups with standard methods. Among pairs of known half‐sibs, LRs ranged from a low of 0.1 to a maximum of 3763. Among random and shuffled pairs, LRs ranged from a low of 0.0001 to 12 for shuffled pairs or 42 for random pairs. LRs of greater than 2 were produced in 8 instances among random pairs and in 4 instances among the shuffled pairs. Overall, results suggest that half‐sib indices of 30 or greater are fairly characteristic of individuals who are related as half‐sibs. In contrast, half‐sib indices of 0.1 or less are fairly characteristic of unrelated individuals who claim to be half‐sibs. LRs falling between 0.1 and 10.0 are uninformative, as this region represents the overlap in the LR distributions produced from the true and false half‐sib groups when the Identifiler multiplex kit is used for testing.