While the average customer understands that DNA paternity test results are delivered according to percentages (e.g. a 99% or 0% likelihood of paternity), the question often remains, “How accurate are these numbers?”

The Paternity Index for each child-father match represents the likelihood of paternity versus a random man of similar ethnic background. DNA Worldwide calculates the Paternity Index using the putative father’s ethnicity and allele frequencies for the matching allele.

If the matching alleles are relatively uncommon, the Paternity Index will be high, providing the strongest evidence of a paternal relationship. Where matching alleles are among the most common, the Paternity Index will be lower, suggesting the possibility of random matching between unrelated individuals; such correlations are much weaker.

Once the Paternity Index has been generated for each matching allele, the Combined Paternity Index is calculated by multiplying all Paternity Indices together.

A result that exceeds 100 indicates a 99% or greater probability that the man is the child’s biological father. Paternity test CPI values can extend into the millions, yielding paternity probabilities of 99.9999% and higher.

Even a single mismatch will result in a CPI of 0—generally excluding the possibility of fatherhood in the putative individual; two or more mismatches add certainty to this exclusion.

However, in some rare circumstances one—or more—mismatches could still permit inclusion of the purported father as the biological father. Occasionally a natural mutation can occur through which a child’s allele will differ from that of his father. For example, a father may possess alleles measuring 10 and 12 at a particular marker, but through mutation, he might pass an 11 or a 13 to his child (mutations tend to move in single steps from original alleles—generally in an upward direction).

In the rare case in which an alleged father matches at all other loci—with the mismatch differing by a single step—DNA Worldwide performs additional analysis to verify the likelihood of this difference being a true mismatch, versus the result of a mutation. In such cases, DNA Worldwide consults special databases that store mutation rates and allele frequencies. Additionally, DNA Worldwide may perform other DNA testing to confirm the mutation or mismatch. Once completed, DNA Worldwide offers a twice-tested, double-checked result; this is the percentage of probability that the consumer is hoping to see.

Terrence Ogden is an investigative writer. For more information on DNA paternity testing in UK or DNA testing kits, he recommends you to visit http://www.dna-worldwide.com/