Unknown DNA Match? What to Do Next

When a DNA analysis tool returns an unknown or conflicting match, the first step is to pause and verify the data before making any decisions. You should re-check the raw DNA file, confirm the tool’s parameters, and cross-reference the result with at least one other independent analysis platform before drawing conclusions.

Why DNA Tools Sometimes Return Unknown or Conflicting Matches

DNA analysis tools, whether they are direct-to-consumer ancestry tests or third-party raw data interpreters, rely on comparing your genetic markers against reference databases. These databases are built from specific populations, and the algorithms they use can differ significantly. An “unknown” match often means the tool could not find a sufficiently similar segment in its reference set, which can happen if your ancestry is underrepresented, if the DNA sample quality is low, or if the tool’s threshold for a match is set very high. Conflicting matches occur when two tools use different reference panels, different statistical models, or different versions of the same reference data. For example, one tool might report 20% Scandinavian while another reports 15% British, simply because the two tools define those regional categories differently.

Immediate Steps to Take

When you see an unknown or conflicting result, do not panic. Follow these steps in order:

• Check the raw data file: Ensure the file you uploaded is complete and from the correct person. A corrupted or truncated file can cause errors.
• Review the tool’s parameters: Look at the settings you used. Some tools let you adjust the confidence threshold, the minimum segment length, or the reference population. Lowering the confidence threshold can reveal matches that were previously hidden.
• Re-run the analysis: Sometimes a temporary server error or a glitch can cause a bad result. Re-running the analysis after a few hours can resolve this.
• Upload to a second independent tool: Use a different platform that accepts raw DNA data (such as GEDmatch, MyHeritage, or FamilyTreeDNA) to see if the result is consistent.
• Contact support: If the result still seems off, reach out to the tool’s support team with your file and a description of the issue. They can check if there is a known bug.

How to Compare Results Across Tools

Comparing results from different tools is not like comparing apples to apples. Each company has its own reference panel, which is a set of DNA samples from people who are considered representative of a particular region. For example, 23andMe’s reference panel might include more samples from a specific part of Europe than AncestryDNA’s. When you see a conflict, look at the confidence percentage each tool assigns to a match. A match with 90% confidence is more reliable than one with 50%. Also, pay attention to the genetic distance or shared centimorgans (cM) for relative matches. A conflict in ethnicity estimates is common and not necessarily an error, but a conflict in a close relative match (like a parent or sibling) is more serious and warrants further investigation.

Common Causes of False or Conflicting Matches

Several factors can lead to inaccurate or contradictory results:

• Low DNA quality: If the sample was degraded or the genotyping chip had a low call rate, the data may have missing or incorrect SNPs, leading to errors.
• Identical by chance (IBC) segments: Small segments of DNA can be shared by people who are not actually related due to common ancestral populations. Tools often filter these out, but if the threshold is too low, they can appear as matches.
• Genetic recombination: Each generation shuffles DNA, so the segments you inherit from a grandparent are not the same as those your sibling inherits. This can cause a tool to miss a match that is actually there.
• Reference panel bias: If the tool’s reference panel lacks diversity, it may assign your DNA to the closest available population, even if that is not accurate.
• Algorithm differences: Some tools use a maximum likelihood approach, while others use a nearest-neighbor algorithm. These can produce different results on the same data.

How to Choose a Reliable DNA Analysis Tool

If you are considering using a DNA analysis tool, especially for health or deep ancestry, research the tool’s methodology. Look for tools that publish their reference panel details and their validation studies. For raw data interpretation, choose tools that have been around for several years and have a large user base. Check if the tool allows you to download your raw data, which is a good sign of transparency. Avoid tools that make bold claims about predicting your exact ethnicity or health risks without caveats. Also, consider the privacy policy: some tools share your data with third parties, so read the fine print before uploading.

What to Do If You Get a Conflicting Relative Match

A conflicting relative match is different from an ethnicity conflict. If one tool says you have a first cousin match and another says no match, that is a serious discrepancy. First, check the amount of shared DNA in centimorgans. A first cousin typically shares about 850 cM, but the range is wide (575-1300 cM). If the match is below 100 cM, it could be a distant relative or an IBC segment. If the conflict involves a close relative (parent, sibling, grandparent), you should consider the possibility of a non-paternity event or a mislabeled sample. In that case, contact the testing company’s support and ask for a manual review. Do not make any assumptions about family relationships without confirming with the other person and, if necessary, a professional genetic counselor.

Costs and Safety Considerations

Most direct-to-consumer DNA tests cost between $50 and $200, but third-party analysis tools often charge a small fee or are free for basic features. The cost is not necessarily an indicator of accuracy. Safety is a bigger concern: your DNA is extremely personal data. Before uploading to any tool, check whether the tool allows you to delete your data at any time, and whether they share data with law enforcement or research partners. In the United States, the Genetic Information Nondiscrimination Act (GINA) protects against discrimination by health insurers and employers, but not by life insurance or long-term care insurance companies. Always read the privacy policy and consider using a pseudonym if you are concerned.

Frequently Asked Questions

Can an unknown match be a false negative?

Yes, an unknown match can be a false negative. This happens when the tool fails to detect a real match because the shared segment is too short, the DNA quality is low, or the reference panel does not include the relevant population. If you have a known relative who also took a test, and the tool does not show them as a match, that is a red flag that the tool is missing something.

Why do two different DNA tests give me different ethnicity estimates?

Ethnicity estimates are just that—estimates. Each company uses a different reference panel and a different statistical model. Your DNA is the same, but the way it is compared to reference populations varies. Differences of 10-20% in a single region are common and not a cause for concern.

Should I use a third-party raw DNA analysis tool?

Third-party tools can provide additional insights, but they are not regulated by the FDA or other health authorities. They can be useful for genealogy and for finding matches across multiple databases, but be cautious about health-related predictions. Always verify any health-related findings with a medical professional.

How can I tell if a DNA match is real or just a coincidence?

Look at the size of the shared segment. A match of 20 cM or more is more likely to be a true genealogical match, while smaller segments (under 10 cM) are often identical by chance. Also, check if the match appears in multiple tools; if it does, it is more likely real.

What should I do if a DNA test reveals an unexpected family relationship?

This can be emotionally challenging. Take time to process the information. Consider reaching out to a genetic counselor who can help you understand the implications. If you decide to contact the person, be respectful and prepared for any reaction. Do not share the information with others without the other person’s consent.

Can I delete my DNA data from a tool after analysis?

Most reputable tools allow you to delete your data, but the process varies. Check the tool’s privacy settings. Some tools keep your data for research even after you delete your account unless you explicitly opt out. Always download your raw data before deleting, as you will not be able to retrieve it later.

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