Technical progress in parentage analysis.

At the turn of the 20th century, Mendel's laws were found to be applicable to human blood groups. Within two decades, blood group genetics were applied to problems of parentage. Expansion of immunohematology into leukocyte antigen identification produced the single most informative, expressed polymorphism. About the same time, analysis of a great number of soluble protein polymorphisms followed advances in electric separation methods, enzymology, and immunochemistry. As new, independent loci were discovered, the power to exclude the falsely accused increased, and it became possible to apply Bayesian principles to determined probabilities of biologic relationships. The revolution in nucleic acid technology has dramatically improved analysis and statistical inferences. By the turn of the 21st century, laboratories should be able to determine biologic parentage with virtual certainty.

HLA in kinship determinations among Haitian immigrants.

Immunogenetic study of alleged first-degree relatives was undertaken among 258 prospective United States immigrants from Haiti. Methods involved serotyping red cells for ABO, Rh, and MN antigens and typing leukocytes for HLA, A, B, and C locus antigens. Kinship was definitely excluded in a relatively low 4.2% of cases involving putative parents and children. Among cases involving alleged siblings, estimates of fraud appeared slightly higher, but the method is suspect because even in true sibships, there may be an absence of obligatory gene markers. Data suggests that some cases involved half-siblings rather than fraud. Of demonstrated exclusions of parent or child, HLA detected the lack of kinship in 87.4% versus 16.9% by red cell typing. However, there were cases in which exclusions were found by red cell methods alone; furthermore, red cell plus HLA typing allows for a calculation of probability of kinship that is analogous to calculations in paternity studies. Together, the red cell and leukocyte systems offer a prior probability of exclusion of parent-child relationships in 91.3%.

Laboratory evidence of unsuspected parental consanguinity among cases of disputed paternity.

A search was conducted to find evidence of possible incestuous unions between the biologic parents of children involved in 2500 paternity cases. Suspicion was raised when either (1) a mother and her child possessed identical HLA phenotypes, or (2) the child appeared to be possibly homozygous for one maternal haplotype (i.e., one of the child's HLA haplotypes was a blank). These mother-child HLA-haplotype dualisms (MHDs) occurred in 5% of all cases. Frequency of exclusion of the accused men in cases demonstrating MHD, was compared with the remaining paternity cases. No significant difference was found in overall exclusion rates between MHD cases and controls when exclusion produced by HLA and red cell antigen systems were observed. However, there was a greater rate of exclusion in MHD cases when comparing exclusions produced by red cell antigen systems regardless of whether HLA tests excluded paternity (p less than 0.025). MHD cases involving teenaged mothers differed from control cases in frequency of exclusion of paternity only on the basis of red cell antigen phenotyping (p less than 0.005). The HLA system's usefulness in paternity testing is diminished when there is MHD; multiple, independently-inherited systems are relatively more useful in these circumstances. The search method detects only half of potential incest cases; proof of incest requires more extensive testing for homozygosity among other polymorphisms. Since calculations of likelihood of paternity are inappropriate in cases involving close consanguinity, detection and follow up studies are important. Data suggest that one-fifth of MHD cases may involve first degree consanguinity and that the incest rate among paternity cases may be as high as 2%.

Utility of HLA and six erythrocyte antigen systems in excluding paternity among 500 disputed cases.

Six erythrocyte antigen systems and the HLA system were evaluated to establish their practical value in 500 cases of disputed paternity. The actual results were very close to predicted values. HLA testing is expected to detect 92% and red cell testing is expected to detect 67% of men falsely accused in paternity suits. The findings of this study show that HLA detected 94% and red cell testing detected 69% of 107 men falsely accused in 500 paternity cases. In order of sensitivity, Rh, MNSs, and ABO were the most useful erythrocyte marker systems. There were six out of 107 cases in which exclusions would have been undetected if red cell typing had not been performed. Five of the six cases involved "common" HLA haplotypes.