How to Interpret Your DNA Paternity Test Result

How To Interpret Your DNA Paternity Test Report

A DNA test for paternity will in general result in a conclusive answer. The result of the test will either completely exclude the alleged father as the biological father with 100% accuracy. Alternatively the results will 'include' the alleged father, that is, the alleged father is ‘not excluded’ from being the biological father. All our DNA tests are based on the analysis of 15 genetic loci (the 16th gene is the sex gene) which are analysed independently to generate a paternity index. The sum of these individual indexes is combined together to obtain the Combined Paternity Index (CPI).

What Is The Combined Paternity Index?

The Combined Paternity Index (CPI) is obtained from the individual Paternity Indices obtained for each locus analysed. The CPI is calculated on the basis of the commonality between the genetic information obtained from the analysis against the general population, thereby generating the likelihood of paternity with a maximum result of 99.99999% Probability of Paternity. In our DNA paternity test results both the Probability of Paternity and CPI are quoted.

The DNA Test Report In More Detail

Once the laboratory obtains the DNA from the samples sent by the client, the DNA will be analysed to look at certain regions of the chromosomes that will vary in length from one individual to another. Each of these points is called a locus and our tests are based on the analysis of fifteen of these genertic loci. Scientific studies conducted on these loci have identified within a large population many different size fragments (also called alleles) associated with each locus.

The DNA test report presents on the first coloumn on the left each of the 16 genetic loci analysed. Each person has two copies of a chromosome inherited one each fromeach 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 used to match the profiles between the persons participating in the test.

As an example, if a child has two alleles labelled as 14 and 18, and the mother has two alleles labelled 16 and 18, then the child will have inherited the 18 allele from the mother and the allele 14 from the father. Therefore, the man tested as the alleged father must possess this allele to be able to confirm him as the biological father. This comparison process is repeated for each of the loci analysed. If the alleged father does not have the matching allele at every locus tested, then he will be excluded 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 we obtain a Probability Percentage of 0%, then this will determine that the DNA of the alleged father is not consistent with that of the child. He will therefore be excluded from being the biological father. If however, there is consistency in the matching of the alleles, then the Probability of Paternity percentage can exceed over 99.9999%+.

If you require more information about how to interpret your DNA paternity test result we suggest that you Contact Us directly.