A critical analysis of paternity determination using HLA and five erythrocyte antigen systems.

Five hundred and thirty-seven cases of disputed paternity in North Carolina were tested for five erythrocyte polymorphisms, HLA antigens, or both. The data were analyzed to evaluate the ability of the tests to exclude the alleged father or to include the alleged father as the biological father. Incompatibility between the phenotypes of the alleged father, and those of the mother and child, were found in 40.6% of black males and 30.3% of white males (P less than 0.005). The rates of exclusion appeared to vary between countries in which the cases originated, although the significance of the differences could not be determined because of the small sample size. Using a Bayesian approach and 0.5 as the prior probability of paternity, we calculated the posterior probability of paternity for HLA and five erythrocyte systems combined as well as for HLA and erythrocyte systems separately. The probability of paternity values based on the combined HLA and RBC tests exceeded 95% in 299 of the 345 nonexcluded cases as compared to only 218 cases based on HLA tests alone and 36 cases based on erythrocyte tests alone. We conclude that in approximately 10% of paternity cases in the population served by this laboratory, the information obtained is inconclusive. To resolve these cases, additional polymorphisms and/or a panel of genetic tests systems which can provide greater than 95% probability of exclusion is required.