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Understanding How to Read a Paternity DNA Test

Aug 18, 2019 | Paternity

Understanding How to Read a Paternity DNA Test

DNA Diagnostics Center (DDC) is the world leader in DNA Paternity Testing at home, performing over one million paternity tests each year. Each test is processed at our state-of-the-art facility outside Cincinnati, providing online results as soon as 24 to 48 hours after the samples arrive at our lab and go into testing. This detailed paternity test report contains scientific as well as legal terms to describe our highly precise process and your results. Here’s a breakdown of the different sections in the report and what they mean for you and your family.

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Understanding Your Paternity Test Report

When you receive your DDC paternity test results, it may seem overwhelming at first. The report includes scientific data, terms, and complex figures that might feel difficult to interpret. This section aims to break down the report and make the results more understandable. Whether you’re seeking closure, legal confirmation, or personal clarity, understanding your test results is a crucial part of the process.

DDC Paternity Test Results Report Overview

Your DDC paternity test results report contains several key sections, each displaying important information. These sections include:

  1. Genetic System Table (Locus/Allele Sizes Chart)
  2. Combined Paternity Index
  3. Probability of Paternity
  4. Test Conclusions

Each section serves a specific function in helping to establish paternity, providing you with both statistical data and a clear conclusion about whether or not the tested individual is the biological father.

Genetic System Table

The Genetic System Table is one of the most crucial parts of your paternity test report. This table contains DNA data collected from all parties tested, and it plays a pivotal role in determining whether a biological relationship exists between the alleged father and the child.

What is a Locus and an Allele?

A locus is simply a location on a chromosome where a specific gene or marker is located. Each person has two alleles at each locus—one inherited from their mother and the other from their father. The Genetic System Table lists the loci and alleles for the child, the mother (if tested), and the alleged father.

The alleles are compared across all parties to determine whether the alleged father shares a genetic match with the child. If the mother’s DNA is tested, her alleles will also be considered in this comparison to ensure accuracy. This comparison is essential for excluding non-matching DNA segments and verifying potential matches with the alleged father.

How to Read the Genetic System Table

At first glance, the table may appear to be a list of numbers and terms that make little sense. However, each number represents the size of the alleles for the individuals being tested. In most cases, at least one allele in each locus from the child must match one allele from the alleged father. For example, if the child inherits a “16” allele from the mother, the remaining allele must match one from the father for the paternity test to indicate a match.

The table also includes a locus called Amelogenin, which is a marker that indicates the sex of each individual. A pair of X alleles indicates a female, while an X and Y combination indicates a male.

Paternity Index: Understanding the Statistics

The Paternity Index (PI) is another important part of your paternity test report. This number, which appears in the Combined Paternity Index section, represents how strong the match is between the alleged father and the child at each DNA locus.

The Paternity Index at each locus is calculated based on the likelihood that the child’s DNA was inherited from the alleged father, as opposed to a random, unrelated man from the same population group. The Combined Paternity Index (CPI) is the cumulative product of all these individual indices. The higher the CPI, the more likely the alleged father is the biological father.

For example, a Combined Paternity Index of 533,475, as shown in the report, means that it is 533,475 times more likely that the tested individual is the father than a random, unrelated man with a similar racial background. It’s important to note that this number will vary depending on the case and the strength of the DNA match.

Probability of Paternity: What Does 99.999% Mean?

The Probability of Paternity is a figure that reflects the likelihood of the tested individual being the biological father of the child. This probability is calculated from the Paternity Index and expressed as a percentage. In most cases, when a father is “not excluded” as the biological father, this probability is 99% or higher—often exceeding 99.999%. This is commonly referred to as a near-certain result, and the higher the percentage, the more likely the man is the biological father.

However, it’s important to note that no DNA test can offer a 100% probability of paternity. The calculation is based on statistical models, meaning there will always be a very small margin of error. That being said, a probability of 99.999% or higher is considered legally and scientifically conclusive.

Test Conclusions: Father or Not?

The Test Conclusion section of your report will clearly state one of two outcomes:

  1. Is not excluded as the biological father: This means that the alleged father is most likely the biological father, based on the DNA evidence.
  2. Is excluded as the biological father: This means that the alleged father is not the biological father, as the DNA analysis does not support paternity.

These conclusions are straightforward, and if you are unsure about their implications, the DDC team is available to provide further clarification.

Frequently Asked Questions: Addressing Common Concerns

What happens if there is a mismatch?

In some cases, there might be a mismatch between the child’s and alleged father’s DNA at a specific locus. You might wonder how this can happen if the Probability of Paternity is still over 99%. The answer often lies in the concept of genetic mutations. It is possible for a mutation to occur in one of the alleles, leading to a mismatch in the results. However, our experts take these mutations into account when calculating the final paternity probability. This means that even with a mismatch, the man can still be considered the biological father.

Can paternity test results be wrong?

Our testing process at DDC is extremely thorough. Each sample is analyzed twice by different teams to ensure there is no possibility of human error. If the test results exclude the alleged father, there is a 0% chance of him being the biological father. If the results indicate a high probability of paternity, the accuracy is nearly 100%. However, if two possible fathers are close relatives, such as brothers, additional testing may be necessary to avoid ambiguity due to the similarity in their DNA. It is important to let us know if there are two closely-related possible fathers.

Why are there no names on my report?

For at-home paternity tests, names are not included in the report. This is because the samples are provided by the customer, and we cannot independently verify the identity of the individuals submitting the samples. Each sample is instead labeled with an identifying number. In contrast, a legal paternity test, which requires court-admissible results, includes both the names of the individuals and company branding to verify the chain of custody.

Paternity Testing During Pregnancy

For expectant mothers who need paternity answers before the child is born, DDC offers a Non-Invasive Prenatal Paternity Test. This test analyzes the baby’s DNA, which is naturally present in the mother’s bloodstream during pregnancy, and compares it to the alleged father’s DNA. While this test contains different data from a postnatal paternity test, the report is similarly structured, ensuring results are accurate and easy to interpret.

About DNA Diagnostics Center (DDC)

DNA Diagnostic Center is the world leader in paternity and relationship testing. Our services are trusted by healthcare professionals, government agencies, and individuals globally. With over one million paternity tests conducted annually, DDC is committed to providing reliable, accurate, and confidential testing services.

Whether you’re looking for personal answers or need legal proof of paternity, DDC offers expert guidance and support every step of the way. Have more questions? Don’t hesitate to call us, we’re here to help.

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848 Comments
  1. Chevon

    Chevon please help me on my question please cause I’m really worried bout this probability please or do I need to call somebody please answer my question

    Reply
    • DDC

      Hi, Chevon. We are researching your question right now. If we can answer here without violating HIPAA regulations, we will. Otherwise, we’ll contact you directly, OK?

      Reply
    • DDC

      There is only one test in our system associated with these participants. It looks like you’ve called us multiple times about the results of the test you did with us; as I’m sure you understand, if you did another test with a different company, we cannot comment on those results.

      Reply
  2. Sanjay

    Me (Husband), my wife and my child got tested Paternity Test with 24 Markers. All the Markers are exactly matching.
    The result is ‘Can not be exclude as Biological Father’ with Paternity Index : 99.99999999% & combined Paternity Index : 38,164,564,715.
    There was another Alleged Father who is not tested but we both are no way related to each other. He is not agreeing to give his mouth swab for test.
    I am bit worried about my test results. are my test results are okay without his test results as we both are no way related to each other?
    My heart is pumping like anything and bit nervous and anxiety.Please help.

    Reply
    • DDC

      Your probability of paternity is extremely high, so there’s nothing to worry about.

      Reply
      • Sanjay

        Thank You so much for quick response. Now I am cool down and relieved from pressure.

        Reply
        • DDC

          You’re very welcome. Take care!

          Reply
      • Sanjay

        Hi DDC,
        I have requested Alleged Father 2 for Paternity test. 15 Markers are not matching out of 24 Markers and Paternity probability is 0%.
        My earlier Paternity test are all 24 markers are matching with 99.99999999% Probability with combined Paternity Index : 38,164,564,715. I am very much happy to see these results. Thank You for with me in difficult times.

        Reply
        • DDC

          So if I understand correctly, you got an inclusion on your test while the other possible father was excluded as the biological father. We are pleased that you are happy and that we were able to confirm you biological relationship.

          Reply
  3. Dee

    Dee, hello

    Reply
    • DDC

      Hello, Dee. We cannot locate any test in our system that matches the email address you provided for this comment, and we cannot publish that comment unless we can locate the cases in question. That way, we can address your concerns properly. You’re welcome to call us at 800-831-1906 if that’s easier for you.

      Reply
  4. Adam

    Adam ok thanks I just wasn’t sure so the names that are on ur samples is what the lab uses right cause I want to make sure I had enough swabs in to receive these results

    Reply
    • Adam

      Adam message

      Reply
    • DDC

      You’re good, Adam. Your results are correct for the samples you submitted.

      Reply
  5. Adam

    Adam I thought the lab was in Ohio that was the address on my package when I mailed it off Fairfield ohio

    Reply
    • DDC

      Yes. Fairfield is a suburb of Cincinnati, Ohio.

      Reply
  6. Adam

    Adam I had test done through identigene and it ask to use 4 swabs for each person I’m just wondering if everything was use correct for the results I received

    Reply
    • DDC

      Hi, Adam. HomeDNA Identigene is one of our brands, and all testing is performed here at our highly-accredited lab in Cincinnati. Each test is performed twice (by independent teams) to ensure accuracy. You can be sure your results are correct for the samples you submitted to us.

      Reply
  7. Jamie

    The man who could potentially be my father is deceased. I have no contact with his brothers or sister. Would the test still be accurate if I used the DNA from one of his children? If not what is the best way to get an accurate result

    Reply
    • DDC

      Hi, Jamie. The optimum way to do a half-sibling test is to test one of his children, you, and both your mothers.

      Reply
  8. Alex

    Locus Child Father PI
    D8S1179 13,14 11,13 0.75
    D21S11 30,32 29,31 0.0040 *
    D7S820 8,10 10 1.95
    CSF1PO 12,11 12 1.38
    D3S1358 14,15 15,17 0.91
    D13S317 8,13 13,14 2.14
    D16S539 11,13 10,11 0.79
    D2S1338 23,24 19,24 2.17
    D19S433 13 13 3.92
    vWA 16,18 18,19 1.23
    TPOX 8,10 8 0.95
    D18S51 12,16 12,14 2.20
    D5S818 9,14 12,13 0.0024 *
    FGA 21,23 21,22 1.39
    PROBABILITY OF PATERNITY: 0.099% COMBINED PATERNITY INDEX: 0.00099
    So obviously there are the two non matches in the results above. my question would be about the other four that are zero percent. If there is a match for one of the numbers, why are they not comparable with the other numbers of greater than 1.0?

    Reply
    • DDC

      Hi, Alex. I asked our Chief Science Officer to look at your data, and this is what he said: “The CPI is inconclusive. There are 2 genetic inconsistencies (exclusions). Each exclusion is a one step exclusion where there is a one number difference between the child and alleged father’s numbers, consistent with a double mutational event. This case needs additional testing to resolve; something we can provide (only 14 loci were examined here and we and test more than 30). It also may require having the mother included in the testing, if possible. Double mutations do occur. We see several double mutational events each month.”
      It looks like further testing would be a good idea, Alex.

      Reply
      • Alex

        Whoever is doing this blog, I truly appreciate your work. This whole testing procedure (through a different company) and the results have been so disheartening personally and has put a huge strain on my relationship and trust with my wife. I’m going to go through DDC this time and hopefully put this to rest for good. She denies any infidelity of any kind and i’m more the type to believe science. If your lead person explanation of those results are correct, you have put a glimmer of hope into my life and my family’s as well. Thanks for following up on my question, for real, thank you!

        Reply
        • DDC

          Thanks for your kind words, Alex, and you’re most welcome. Happy to help! If you have additional questions, you’re welcome to reach out here again, or you can send a private Facebook message to our page: @ddcpaternity.

          Reply
  9. Sar

    Sarah, so u think my results I received for my son were accurate even tho it was a piece of mind test cause what would it be if not I received a 99.99998 result I just scared that I got wrong results cause my son has no favor ness but I hope that they wouldn’t send out wrong results in just worried cause this my first time doin this and I brought my test from Walgreen the homedna identigene

    Reply
    • Sarah

      Sarah hello I didn’t get a answer to my comment from the 7th of December

      Reply
      • DDC

        Sarah, you needn’t worry…you can trust your results.

        Reply
  10. Sar

    Sarah, can father and child swabs get mixed up when both are males

    Reply
    • DDC

      It wouldn’t happen in our lab. But let’s say someone mixes up the sample envelopes at home before sending in their samples. We don’t check for age…just for gender. So even if we test the son as the “father” and the father a the “son,” the results will be the same: they share (or don’t share) a father/son biological relationship.

      Reply

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