Understanding your Paternity Test Results

So you have participated in a DNA Test and the test informs you or in the worst case scenario - you simply get an email - that the result is 99.99% Probability of Paternity  (POP)and your first question is why is it not 100% accurate?  Genetic testing to confirm biological relationships can never be 100% because the only 100% match of your DNA is yourself?  Get it?  If we do a DNA test on you and another individual and the Probability returned at 100% - the other individual would have to be yourself or your identical twin.  The genetic relationship expressed in terms of a percentage between two people (or more) should at least match 99.9% in the case of paternity but will never be 100%.  The other incidence in which you can expect 100% is in the case of exclusion or you are not the father.  If the man tested, is not biologically related at all to the child in the test, then the results return with 0% Probability which means that there is no doubt you are not genetically related to the child with 100% accuracy. 

Let me try this another way.  When you take a paternity test - usually the child is tested as well as the mother and an "alleged father".  The reason we test the mother is to clearly identify which portion of the DNA belongs to the mother - so that the remaining strand of DNA should match the tested "alleged" father.  That means, that only half of the child's DNA comes from the father (sperm) and half from the mother (egg).  OK - so now you ask why is the test expressed in terms of 99% and not 50% - again, not having a full understanding of what all the numbers on the test refer to gives you the impression that the POP should be different than what is returned to you.  The test returns with a 99% or higher - because we test specific markers and if your genetic markers match the child's genetic markers at 13 different markers - you are a genetic martch 99% more than any other man tested, from the same ethnic background.   Not having the mother to participate in the DNA test, does not mean we cannot confirm or deny paternity but if the mother is willing to participate in the test than including mom provides more conclusive results. 

If you receive Paternity Test results with a number that is less than 99% Probability of Paternity there are few points to consider:

1.)  Ask the DNA collector (please use a professional DNA collector) if extended analysis can be completed to try to bring the Probability up to 99%.  No one will offer additional DNA testing for free so expect at least a nominal fee.  If the mother was not included in the test, try to bring in mom for additional testing.  If the mother is not available for testing, bring in her biological sisters and/or biological mother or other siblings of the mother.  If the father is not available for testing, bring is his biological brothers, father, siblings.  Testing two children can also confirm whether they share the same biological parents or only one biological parent.  See our Full vs. Half vs. Unrelated Siblingship Testing blogs.  Often times, we test siblings for the Department of Homeland Security or U.S. Embassies to complete Family Based Immigration Visas.  The same tests can be used to obtain other benefits.   

2.)  Ask yourself, is there a possibility that another family member (brother, father, uncle - male cousin related only through your father) could have fathered the child?  If you receive a DNA Test result with numbers less than 99% but higher than 0% everyone may benefit from including other male family members in additional testing to confirm paternity.  In the end, the child benefits by knowing exactly who is the father - starting life out on the same stable footing as other children and having knowledge of medical background is increasingly important as we move toward personalized medicine. (DNA is now being used to prescribe medications for that have different benefits based on a DNA Test.)

3.)  Ask the DNA collector to perform another collection, using a different laboratory, and compare the results.  If using a second laboratory brings the results up and over 99%, ask for an explanation from the first laboratory.  As always, proper DNA testing, by a properly accredited DNA testing laboratory is not free - but it is not cost prohibitive these days either.   

4.)  There is a very slight chance, that your DNA has a mutation that did not get expressed in your children's - only further extended analysis will confirm paternity - this is rare in any case.

Questionable DNA Test results also brings to mind the over the counter kits or off the internet home kits, which may initially save money but long term may result in doubts and/or double testing because of the misunderstanding of the reports and because of the method of collection/mailing/results return.  Always, have your DNA Paternity Tests and other Biological Relationship Tests performed by an accredited facility with a direct employee of the DNA testing laboratory or a agent acting on behalf of the laboratory and ask for proof of the agent's agreement with the laboratory in use.  Someone who purchases over the counter or off the internet kits and represents themselves as a DNA collector - has limited investment in performing the collection accurately, limited access to up to date knowledge within the genetic testing field, has limited interest in submitting samples securely sealed and free of contamination and returning the accurate and reliable results to the correct parties with any interpretation or explanation.  A local, private DNA collector is usually able to explain the results and is the same person to whom you can return 3 months later with questions and/or additional parties to test. 

DNA Testing, although a joke on TV shows and Tina Fey movies today, is not really a joke.  Imagine not knowing your biological father - if not for understanding your roots at least knowing the genetic diseases that exist in your family and taking care to avoid behaviors that contribute to the onset of those genetic diseases is important.  See our Predictive Genetic Blog, to determine if you are genetically at risk for more than 25 different diseases - in the event you do not know your biological parents. 

Always ask your DNA collector any necessary questions so that you are comfortable with the results and confident that your DNA collection was done properly, privately and free from contamination.