Analysis of paternity. The use of HLA and red cell antigens.

Over a 6-year period, 866 cases were analyzed for disputed parentage. In 194 cases (22%), the alleged father was excluded as the biological father. One hundred and eight-one cases (93%) were direct exclusions, and 13 cases (7%) were indirect exclusions. Ninety-two percent of falsely accused men were identified by typing for HLA antigens alone. Exclusions based solely on red cell data occurred in 8 percent of the cases. When only HLA testing was performed, 177 of 362 (43%) cases had a probability of paternity of greater than or equal to 95 percent. When both HLA and red cell typings were performed, 110 of 160 (69%) cases had a probability of paternity of greater than or equal to 95 percent. No significant differences in the proportion of exclusions or proportion of alleged fathers with a probability of paternity of greater than or equal to 95 percent were observed between Caucasians or blacks. We conclude that typing for HLA antigens provides the most powerful data for excluding or including an alleged father. However, typing for red cell antigens adds significant data in excluding a falsely accused man and in determining the probability of paternity at a critical level (greater than or equal to 95%). In addition, the current study suggests that additional assays are needed to identify genetic characteristics of cases with probability of paternity less than 95 percent.