You have your raw DNA file. Now what?
You can look up single variants in public databases. You can run the file through a free tool that lists published research on each variant. Or you can order a whole-genome test that a scientist reviews. The file is accurate for the common markers it covers. Rare health variants in raw data are often wrong, so confirm anything serious before you act on it.
What the file contains
A raw file from 23andMe or AncestryDNA is a text file. Each line is one position in your DNA and the two letters you carry there.
These tests check about 600,000 to 700,000 chosen positions. That is about 0.02% of your DNA. A whole-genome file is much larger and covers about 3 billion positions.
One line means little on its own. To understand it, you need the research on that position, the rest of your DNA and your health history.
Two limits to know before you look
False positives
A raw file can show a rare, serious variant that you do not actually carry. A study in the journal Genetics in Medicine looked at variants from consumer raw data that a clinical laboratory then retested. About 40 percent were false positives.
Arrays are reliable for the common markers they were designed to test. Most errors are in rare variants, the ones most likely to alarm you.
False negatives
An array tests only the positions it was built to test. If a relevant variant sits elsewhere, the file does not show it. A file with no findings can simply mean that position was never tested.
Whole-genome sequencing covers far more positions, so it misses far fewer variants. The results still need someone to interpret them. More on this: Are at-home DNA health tests accurate?
Your options
Look up variants yourself
Public databases such as ClinVar and dbSNP let you look up a single variant. This is a good way to learn. One entry rarely shows conflicting evidence. It also rarely says whether the result applies to people of your ancestry.
Use a free annotation tool
Several free tools match the variants in your file to published research. Their quality varies. They list what has been written about each marker in general. They do not weigh it against your history, your blood tests or your other variants.
Move to a whole-genome test
A whole-genome test starts from a new cheek swab. It covers about 3 billion positions, including rare variants an array cannot see. Your old file stays yours.
Order your test or see what is included.
Informational and educational, not a diagnosis. Bring anything of medical consequence to your physician.
Test once. Keep it for life.
Your DNA stays the same all your life. Adriano De Marino, PhD, reviews every report.
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