What is the Paternity Index (PI) and how is it determined?
The Paternity Index or PI gives the odds that the alleged father with a matching allele is the biological father of the tested child. The frequency of each DNA segment (allele) in the human population varies depending on the size of the allele and the race of the alleged father. The prevalence of allele sizes differs from race to race which makes knowing the race of the alleged father important for statistical analysis. Databases are available for Caucasian, Black, Hispanic, and Asian races. If the race is not certain, we will use the lowest PI of all available races. This is a conservative approach for calculating the probability of paternity (POP). The frequency of an allele is determined by how many individuals in that database have an allele size, divided by the total number of individuals in the database. The result frequency is used to calculate the PI.
