How to read a Paternity Test results?

Receiving your paternity test results can feel overwhelming. This post explains how to read and understand the key parts of your DNA report clearly.

How DNA Paternity Testing Works

DNA testing compares specific points on the DNA (called loci) between the child and the alleged father. Each child inherits one segment from the mother and one from the father at each locus. Our lab tests 22 loci to check if the alleged father’s DNA matches the child’s.

Types of Results and What They Mean:

Positive Results (Biological Father Confirmed)

Your report will state that the alleged father “cannot be excluded as the biological father.” This strongly suggests he is the biological father.

Look for these elements in your report:

1. Genetic System Table (Locus/Allele Chart)
   Each of the 22 loci will show alleles for the child, mother, and alleged father. At least one allele per locus will match between the child and alleged father.
2. Combined Paternity Index (CPI)
   This number shows how many times more likely the tested man is the biological father compared to a random man. For example, CPI = 500,000 means he is 500,000 times more likely to be the father.
3. Probability of Paternity
   Typically 99.9% or higher, this percentage shows how certain the test is. Values like 99.9999% indicate near absolute certainty.
4. Conclusion Statement
   The report states clearly that the alleged father is not excluded as the biological father.

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Negative Results (Biological Father Excluded)

Your report will state that the alleged father “is excluded as the biological father.” This means he cannot be the biological father.

Key points in your report:

1. Genetic System Table with Mismatches
   Multiple mismatches (usually 4 or more out of 22 loci) appear between the child’s and alleged father’s DNA.
2. Combined Paternity Index of 0
   No statistical support exists for a biological relationship.
3. Probability of Paternity of 0%
   Confirms no chance the tested man is the biological father.
4. Conclusion Statement
   The report explicitly states exclusion.

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Inconclusive Results

Sometimes results do not clearly confirm or exclude paternity. Reasons include:

• Insufficient DNA in samples.
• Degraded or compromised samples.
• Testing involving close relatives (e.g., brothers).
• Too few genetic markers tested.

The lab may request new samples or additional testing in these cases.

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Understanding Statistical Certainty

Absolute certainty (100%) is impossible because testing every man with a similar background is unfeasible. A probability above 99.9% is considered conclusive proof in legal and scientific settings.

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Mutations and Single Mismatches

Occasionally, a single mismatch may appear even in positive results due to genetic mutations. The lab accounts for this when calculating probability. One mismatch does not automatically exclude paternity if other markers match strongly.

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Need Help?

Call Secure DNA Tests at 888-970-4211 to allow one of our DNA Consultants to assist you with DNA testing needs.