Interpret Your DNA Paternity Test Result

How to interpret your DNA Paternity Test Result

In the majority of cases the DNA Paternity test will give a conclusive result. The tested father will either be excluded from being the father or else the test will confirm he is 'not excluded' from being the biological father. Our analysis are based on the testing of 15 genetic markers. Each marker is analysed separately to determine the degree of relatedness which is shown as a paternity index. All the individual indices are then combined together  to determine the Combined Paternity Index (CPI).

What is the Combined Paternity Index (CPI)

The Combined Paternity Index (CPI) is derived from the Paternity Indices obtained for each genetic locus tested. The CPI represents the likelihood of Paternity and is calculated on the basis of the how common is the genetic information found in your analysis with the general population. The CPI can result in a 99.99%+ Probability of Paternity. Both the CPI and the Probability of Paternity are quoted in the results of the DNA paternity tests performed by easyDNA.

Explaining the DNA Test Result in More Detail

The swabs or other sample sent for analysis will be used to obtain DNA that is then used to locate certain regions of chromosomes that vary in length between individuals. Each of these sites is called a locus and our DNA test is based on sixteen of these loci. Extensive studies of these specific loci have demonstrated that there are a multitiude of different size fragments (alleles) associated with each locus in a large population.

The DNA test report presents on the left hand side each individual loci analysed in the test. Each person has two copies of a chromosome, one inherited from the mother and the other from the father. For each loci, two 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 create matches between the individuals involved in the test.

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.

As explained above, a Paternity Index is obtained for each locus and the combined CPI is used to calculate the "probability of relationship," which is the percentage likelihood that a man with the alleles of the alleged father is the biological parent of the child, as compared to an untested, unrelated man of the same race. This Probability Percentage is presented in the results.

If the results generates a Probability Percentage that is 0%, this will signify that the DNA of the alleged father is not consistent with that of the child and therefore he is excluded as the biological father. If on the other hand the probability Percentage is consistent, then we expect to obtain a result that is in excess of 99.9%+.