Inconclusive Results in Sibling, Avuncular, and Grandparent DNA Testing
Understanding Inconclusive Relationship Results
DNA testing can be a powerful tool for determining biological relationships. However, one of the most challenging outcomes clients face is receiving inconclusive results, especially in sibling, avuncular (aunt/uncle), or grandparent relationship testing. These results can leave people feeling frustrated and confused. In this blog, we’ll explain what inconclusive results mean, how they happen, and what can be done to reach a conclusive outcome.
What Are Inconclusive Results?
An inconclusive result occurs when the DNA testing cannot definitively confirm or deny a biological relationship between the tested individuals. This doesn’t mean the individuals aren’t related—it just means that the data doesn’t provide a strong enough signal to give a clear answer.
Two key factors in determining the results are the Likelihood Ratio and the Probability Percentage.
Likelihood Ratio
The Likelihood Ratio compares the genetic profiles of the tested individuals to determine how likely it is that they are biologically related.
Less than 1.00: Suggests the individuals are not related.
Greater than 1.00: Suggests the individuals may be related, with higher values indicating a greater likelihood of a biological connection.
For example, if the Likelihood Ratio is 3.84, this suggests the individuals tested may indeed be related, but it isn’t definitive.
Probability Percentage
The Probability Percentage measures how likely it is that the tested individuals are biologically related based on shared genetic markers.
99% or greater: Considered scientifically conclusive for a biological relationship.
>90.9%: Considered conclusive based on AABB (American Association of Blood Banks) standards.
10% - 90.8%: This range is considered inconclusive, meaning the data leans one way but not strongly enough to confirm a relationship.
For example, a Probability Percentage of 79% suggests there may be a relationship between the tested individuals, but it is not conclusive.
Why Do Inconclusive Results Happen?
In sibling, avuncular, or grandparent testing, inconclusive results are more common because these relationships share less DNA compared to parent-child relationships. Additionally, genetic similarities can vary significantly between individuals within the same family line.
How to Achieve a Conclusive Result
The best way to increase the accuracy of the test and push the results toward a conclusive outcome is to add more participants, typically a known parent. For example:
Add a known mother or father: Including one of the parents in the test can provide the additional genetic data needed to raise the Probability Percentage above 90.8% or lower it below 10%, which would give a conclusive result.
The addition of a known parent helps the lab better determine which genetic markers are inherited from the shared relative, making it easier to confirm or rule out a biological relationship.
Next Steps After Receiving Inconclusive Results
If you’ve received inconclusive results, don’t worry. While the current data may suggest a possible relationship, it is not yet definitive. To move forward, you can:
Add Additional Participants: By including a known parent, you improve the chances of obtaining a clear result.
Contact Your Testing Provider: If you’d like to proceed with additional testing, reach out to your provider to set up the next steps.
Moving Forward
Inconclusive results in sibling, avuncular, or grandparent DNA testing can be frustrating, but they don’t have to be the end of the process. By understanding the Likelihood Ratio and Probability Percentage, and by adding more participants to the test, you can often turn inconclusive results into conclusive ones. If you’ve received an inconclusive result, consider the next steps outlined above and consult with your testing provider to reach the answers you’re looking for.
For more information or to add participants to your test, contact us today!