Your DNA paternity test results will refer to the term combined paternity index (CPI). Essentially, the DNA test relies on statistical probability and refers to the probability of the alleged father being the biological father of the child and not another person in a population. The test requires analyzing 20 genetic loci and the index of relationship between the loci is used to calculate the paternity index. The 21st loci is the Amelogenin gene.
Once this is done, the indices are put together to give a combined paternity index which is expressed as a percentage. An individual will be excluded as being the biological father by 100% whilst inclusion of paternity is 99.99%. The inclusion rate is slightly below 100% for reasons of scientific correctness.
For a more through explanation of paternity indexes and test results please visit the section Understanding Your DNA Test Results. Alterntatively visit our frequent questions section by clicking here.