Understanding Your Paternity Test Result

Interpreting the DNA Paternity Test report

When you perform a DNA Paternity test the result will be conclusive in most cases with the result either confirming that the father is 'not excluded' from being the biological father or alternatively it will confirm that he is 'excluded' with 100% certainty. All our DNA tests are performed by analyzing 16 genetic loci. These loci are analysed individually and the resulting index of relationship used to obtain a paternity index. Once all the indices are available they are analysed together to determine the Combined Paternity Index (CPI).

What is the Combined Paternity Index?

The Combined Paternity Index (CPI) is calculated from the Paternity Indices generated from each individual locus and gives an indication of the likelihood of Paternity between the alleged father and child as compared to analysis with the general population. The result of the CPI can go as high as 99.9999%+ but will never be quoted as 100% for scientific correctness. As you can see in the attached sample reports, both the CPI and  Probability of Paternity are shown in the results of our DNA Paternity tests.

In the sample result, you an also see that the DNA test report will show on the left hand column each of the 16 loci analsyed. Every person carries 2 copies of a chromosome, one which he inherits from the biological father and the other from the mother. For each loci, 2 numbers are shown (or one in the case where the alleles are identical (homozygous) representing the size of the allele. These numbers are then used to compare between the persons involved in the testing to see whether they match or not.

Therefore, if the child tested has 2 alleles labelled as 15 and 18, and the mother has two alleles labelled 15 and 17, then the child will have inherited the 15 allele from the mother and the allele 18 from the biological father. Once the test is completed, the analysis will check to confirm if the alleged father has this particulalr allele, and of course to be the biological father the allele must match. The procedure is performed for each loci tested. If the alleged father does not have the matching allele at every locus tested, then he cannot be confirmed as the biological parent.

In the case where there are multiple exclusions, the Probability of Paternity percentage is 0% - thereby confirming that the the DNA of the alleged father is not consistent with that of the child and therefore he is excluded as the biological father. If the probability percentage is consistent, then a result in excess of 99.9%+ is normally obtained.

If you have any queries about how to interpret your DNA paternity test result kindly Contact us directly.