Quick Answer: What Does an Inconclusive DNA Test Result Mean?
An inconclusive DNA test result means that the available genetic evidence does not strongly support one possible relationship over another. This can occur when shared DNA markers fall within overlapping ranges between potential relationships or when insufficient DNA is available for analysis.
Why DNA Test Results Sometimes Come Back Inconclusive
An inconclusive DNA test usually means that the shared genetic markers between the individuals tested fall within a statistical range that cannot confidently confirm or exclude a biological relationship. This occurs most often in complex relationship tests such as sibling, avuncular, or grandparent testing where genetic sharing can overlap between different possible relationships.
What Is an Inconclusive DNA Result?
DNA testing works by comparing genetic markers between individuals to determine the likelihood of a biological relationship.
In some cases, the genetic evidence clearly supports a relationship, such as a parent-child connection. In other situations, the data may fall within a range where the results cannot strongly support one conclusion over another.
When this occurs, the result may be reported as inconclusive.
This means that the laboratory could not determine a clear statistical outcome based on the available genetic data.
Why DNA Test Results Can Be Inconclusive
Several factors may contribute to inconclusive results.
Overlapping Genetic Similarities
Certain biological relationships share similar levels of DNA.
For example, relationships such as:
Half siblings
Full siblings
Uncle and niece or nephew
may sometimes share overlapping genetic patterns. This overlap can make it more difficult for statistical analysis to distinguish between possible relationships.
Learn more about sibling relationship testing here: Sibling DNA Testing.
Limited DNA Available
In some cases, insufficient DNA may be recovered from the submitted sample.
This can occur when:
The sample contains very small amounts of biological material
DNA has degraded due to environmental exposure
The item tested is a non-standard sample
Learn more about non-standard samples here: What Items can be used for DNA testing.
Complex Family Relationships
Some family structures may make interpretation more difficult.
For example:
Close relatives within the same family line
Multiple possible biological relationships
Missing parental participants
Additional relatives may sometimes improve the statistical clarity of the results.
How DNA Test Results Are Interpreted
DNA testing laboratories use statistical tools to evaluate how likely a biological relationship is based on the genetic markers shared between individuals.
Two common statistical values used in DNA relationship testing 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 the result is not definitive.
The likelihood ratio is one of the statistical tools laboratories use when evaluating possible biological relationships.
Probability Percentage
The Probability Percentage measures how likely it is that the tested individuals are biologically related based on shared genetic markers.
These interpretations are consistent with guidelines from the AABB (American Association of Blood Banks).
Typical interpretation ranges include:
99% or greater
Considered scientifically conclusive for a biological relationship.
Greater than 90.9%
Considered conclusive based on AABB standards.
10% – 90.8%
This range is considered inconclusive, meaning the data may lean toward a relationship but not strongly enough to confirm it.
For example, a Probability Percentage of 79% suggests there may be a relationship between the tested individuals, but the result is not conclusive.
When Inconclusive Results Are More Likely
Inconclusive results are more common in relationship DNA testing compared to direct parent-child tests.
Examples include:
Sibling DNA tests
Avuncular DNA tests
Grandparent DNA tests
Because these tests evaluate shared genetic markers indirectly, the results rely heavily on statistical analysis.
Can Inconclusive Results Be Clarified?
In some situations, additional testing may help clarify the relationship.
Possible options may include:
Adding additional family members to the test - usually a know parent, in most cases a mother of a participant.
Testing additional relatives
Submitting higher quality DNA samples
Additional genetic information can sometimes strengthen the statistical analysis and provide clearer results.
Frequently Asked Questions
Does an inconclusive result mean the individuals are not related?
No. An inconclusive result simply means the available DNA evidence could not strongly support one possible relationship over another.
Can an inconclusive DNA test be repeated?
Yes. Additional testing may sometimes provide clearer results, especially if additional participants are included.
Are inconclusive results common?
They are relatively uncommon in parent-child tests but may occur more frequently in complex relationship testing scenarios.
Can non-standard samples cause inconclusive results?
In some cases, yes. If limited or degraded DNA is recovered from an item, it may affect the clarity of the analysis.
Understanding Inconclusive DNA Results
DNA testing provides powerful scientific tools for evaluating biological relationships. Even when results are inconclusive, the analysis helps narrow the range of possible relationships and provides valuable genetic insight.
Understanding how statistical tools like the Likelihood Ratio and Probability Percentage are used can help individuals better interpret their DNA test results and determine whether additional testing may provide clearer answers.
