The number 99.999 on a DNA test result refers to the accuracy or precision of the test. DNA testing companies will often report accuracy levels using percentages or decimal places. A result of 99.999% accuracy means the test is extremely precise and accurate, with a very low margin of error. This level of accuracy gives people a high degree of confidence in the results of their DNA test.
Understanding DNA Test Accuracy
DNA tests work by analyzing a person’s genetic code and comparing it to other DNA samples and ancestry databases. The more DNA data a company has in its databases, the more accurate the results can be. Accuracy is also improved by testing more portions of a person’s DNA and using advanced technology to read the DNA.
Most DNA testing companies report accuracy as a percentage or number of 9s following a decimal point. Here are some examples and what they mean:
| 99% accuracy | 1 in 100 chance of error |
| 99.9% accuracy | 1 in 1,000 chance of error |
| 99.99% accuracy | 1 in 10,000 chance of error |
| 99.999% accuracy | 1 in 100,000 chance of error |
As you can see, the more 9s after the decimal point, the more precise the test. 99.999% is extremely accurate with only a tiny fraction of a percent chance for error.
How Companies Calculate DNA Test Accuracy
There are a few key factors that allow DNA testing companies to provide highly accurate results:
Sample Size
The larger a company’s DNA database is, the more accurately they can pinpoint relationships and ancestry. Companies with databases in the millions or billions can place DNA relatives for customers with a high degree of certainty.
Markers Tested
Most tests look at key ancestry markers across a person’s genome. The more markers analyzed, the more precision companies can achieve. Tests that look at hundreds of thousands of genetic markers provide many data points for comparison.
Advanced Technology
Advanced genotyping chips and sequencing techniques allow companies to accurately read billions of pieces of DNA data. Computer algorithms also help find patterns and calculate probability of specific ancestry and relationships.
Statistical Calculations
DNA companies use complex statistical modeling to determine the probability that a given ancestry marker will show up or that two individuals share a common ancestor. These statistics allow estimates of relationships even from small amounts of DNA data.
By leveraging large databases, extensive DNA markers, and statistical algorithms, companies can achieve accuracy levels of 99.999% and higher for ancestry composition and DNA relative matching.
Limits of DNA Test Accuracy
While highly accurate, DNA tests do have certain limitations:
False Positives/Negatives
Even with accuracy levels over 99%, false positives and negatives are still a possibility. A false negative could fail to identify a real DNA relative while a false positive might show a DNA match where there is none. But at 99.999% accuracy, these occurrences should be extremely rare.
Limited Databases
For certain ethnic populations that are underrepresented in ancestry databases, DNA results may be less accurate. Accuracy improves as companies expand their global databases over time.
Complex Family Trees
With intermarriages and endogamous populations, some DNA relationships can be more challenging to identify accurately, especially distant cousins and genetic admixtures.
Rapidly Evolving Technology
As DNA testing technology continues advancing rapidly, even accuracy levels of 99.999% may become outdated in the future. Results could become more accurate over time.
Achieving Maximum Accuracy
While a DNA test with 99.999% accuracy from a major testing company should provide excellent results for most customers, there are a few ways to potentially improve accuracy even more:
Test Both Parents
By testing both parents as well as yourself, companies have more data points to confirm relationships and inheritance. This can increase accuracy and confidence.
Upload to Multiple Sites
Uploading your DNA data to multiple ancestry sites can maximize your matches across different databases. It also allows cross-checking of results.
Compare Close Family
Having close family members take the same test or upload their data to the same site lets you compare results for consistency. Inconsistencies could indicate an error.
Build Your Family Tree
Combining your DNA results with genealogical research to build out your family tree can help confirm that your DNA matches align with your paper trail.
Example DNA Companies and Their Accuracy
Some top DNA testing companies and their reported accuracy levels include:
AncestryDNA
– Accuracy for ethnicity estimate: 90%+
– DNA relative accuracy: 99.9%
23andMe
– Ancestry composition accuracy: 90-95%
– DNA relative accuracy: 99.9%+
MyHeritage
– Ethnicity estimate accuracy: 90%
– DNA matches: 99.9% accuracy
Living DNA
– Ancestry breakdown accuracy: 90%
– DNA matches: 99% accuracy
As you can see, most major companies report cousin matching accuracy levels of 99.9% or higher, while ethnicity estimates are often 90-95% accurate. This still allows consumers to get a great sense of their ancestry composition and confirm DNA relationships with high probability.
Conclusion
A DNA test result with 99.999% accuracy means an extremely precise and reliable result you can feel confident in. This level of accuracy from a reputable company makes it highly likely your ethnicity estimate reflects your ancestry and your DNA relative matches represent real genetic connections. As DNA testing expands globally and technology keeps improving, accuracy should only increase over time. But for now, 99.999% is an incredibly high level of precision for understanding your genetic genealogy.