Understanding Your Paternity Test Result
When you receive your Paternity test result, you will in most cases have a conclusive result. The result will either confirm that the alleged father is ‘excluded’ as the biological father with a probability of paternity of 0%. Alternatively, the result will confirm that the alleged father cannot be excluded from being the biological father with a 99.99%+ probability. The test is based on the analysis of 21 individual genetic markers. Each marker is analysed to obtain a paternity index. The combination of all the indices will be used to determine the Combined Paternity Index (CPI).
What is the Combined Paternity Index?
As explained above, the Combined Paternity Index (CPI) is obtained from combining the Paternity Indices obtained for each genetic marker tested. The CPI therefore represents the likelihood of Paternity and is obtained on the basis of the how common is the genetic information found in your analysis with the general population. As you can see in our sample results, both the CPI and the Probability of Paternity are shown in the result.
The DNA test report in more detail
Once the samples sent by the client are processed, the DNA material obtained is analysed to locate specific regions of chromosomes that differ in length between one person to another. Each of these sites is called a locus and our DNA test is based on the analysis of 21 of these loci. Studies of these specific loci have shown that there are many different size fragments (alleles) associated with each locus in a large population that give rise to our unique DNA profile.
The DNA test report will highlight on the left hand column each of the 21 loci tested. Each individual has two copies of a chromosome, one inherited from each parent. For each loci, two numbers are presented (or one in the case where the alleles are identical (homozygous) representing the size of the allele. These numbers are then matched between the people involved in the testing.
So, for example, if a child has two alleles labelled as 16 and 19, and the mother has two alleles labelled 16 and 18, then the child will have inherited the 16 allele from the mother and the allele 19 from the father. Therefore the alleged father being tested for paternity confirmation must have this allele if he is to be confirmed as the biological father. This process of comparison 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. The Probability of Paternity percentage will therefore be 0% as there is no chance that he is the biological father. On the other hand if there is a match in all the alleles than this will confirm that they are related and if a probability in excess of 99.9%+ is obtained then he will be confirmed as the biological father.