When you do a paternity test through DNA Diagnostics Center (DDC), you are provided with a detailed report when your results are ready. The language required to be used for paternity test results is scientific as well as legal, and so it sometimes may be tricky to understand. Here’s a breakdown of the different sections in the report and what they mean, in simpler terms.
NOTE: This article refers to the post-natal test results report only. For help understanding a Non-Invasive Prenatal Paternity Test report, please contact our prenatal testing specialists at 800-303-9085 (M-F, 8 am to 5 pm Eastern).
DDC Paternity Test Results Report Overview
Your DDC paternity test results report contains the following main sections, with each displaying important information.
- Genetic System Table (Locus/Allele Sizes chart)
- Combined Paternity Index
- Probability of Paternity
- Test Conclusions
Paternity Test Results: Genetic System Table
The DDC laboratory tests at least 20 genetic markers plus the Amelogenin locus, which shows a participant’s sex. The data for the child’s, the possible father’s, and the mother’s (if she participated) genetic systems are listed on your report in table format. Should additional markers need to be tested in order to strengthen results (as illustrated in the table below), those are also listed.
The child gets one gene on each marker from their mother and one gene from their biological dad. If even one of the child’s markers does not contain an allele that matches the possible father’s, then that possible father may not be the biological father. Using statistics, the Paternity Index (listed as PI in the table) indicates the strength of the match at a particular Locus (genetic marker).
Q: If everyone has two genes on each marker, why is there sometimes only one number showing on the report?
A: In most cases, a single number on the report indicates that both genes are the same number. For example: In the chart above, 22,22 for one of the child’s markers shows as just 22. And, since she is a female with two X chromosomes (X,X), this only shows as a single X.
Paternity Test Results: Combined Paternity Index
The Combined Paternity Index is the number on the left side of the report (in the Interpretation section), directly under the Genetic System Table.
If you are considered the biological father, there is a number listed for the Combined Paternity Index. If you are not considered the biological father, the report shows “0.”
The Combined Paternity Index is an odds ratio indicating how many times more likely it is that the possible father is the biological father than a randomly-selected unrelated man with a similar ethnic background. In the example shown above, this man is 43,450,497 times more likely to be the biological father. This number varies on a case by case basis. The higher this number, the stronger the results.
Q: Can the Probability of Paternity ever be 100%?
A: No. DNA test results are all based on statistics. Quite simply, in order to get a 100% probability, we’d have to test every man in the world with a similar ethnic background to the alleged father being tested. And for obvious reasons, that’s not possible!
Paternity Test Results: Test Conclusions
Test Conclusions are located in the Interpretation section, under the Combined Paternity Index and Probability of Paternity numbers. This paragraph of text contains our DNA scientists’ conclusion about your test.
The report shows one of two conclusions: “is not excluded as the biological father” or “is excluded as the biological father.”
If the conclusion states, “is not excluded as the biological father,” this phrase means the possible father most likely IS the biological father of the child, since all data gathered from the test supports a relationship of paternity. (See sections above for details.)
If the conclusion states, “is excluded as the biological father,” this phrase means the possible father IS NOT the biological father of the child, since all data gathered from the test do not support a relationship of paternity. (See sections above for details.)
Q: My test shows one mismatch between the possible father and the child, yet the conclusion says results are an inclusion, with a probability of paternity over 99%. I thought every location had to match for a positive result, so how does this happen?
A: Chances are good that there was a mutation in either the child’s or the possible father’s genetic code at that location. Analysts take mutations into account when doing their calculations and reaching conclusions. So even if there is a mismatch, the man might still be considered the biological father of the child tested.
Why Aren’t There Names on my Paternity-test Report?
When doing an at-home test, there are no names on the report: only an identifying number for each set of samples and their role in the test (alleged father, child, or mother). We do this because we have no way of verifying whether or not a sample submitted to us belongs to the correct participant, as indicated by the customer. However, if you choose to do a legal, witnessed, chain-of-custody paternity test with court-admissible results, then the report includes both names and our company branding. For both at-home and legal testing, the testing process itself is exactly the same, and you can be sure results are guaranteed accurate for the samples provided to us.
Don’t hesitate to call us at 800-929-0847: We’re here to help.
If you have a general question about the info above, leave a comment and we’ll answer.