How accurate is 23andMe and AncestryDNA?

Wondering how accurate your data is from 23andMe? Trying to decide between Ancestry.com or 23andMe? I recently picked up an AncestryDNA kit to find out how well the data matched up to the 23andMe test that I did a few years ago.

Quick answer: The data from both tests matched up better than I expected.

First, a caveat: I’m not a genealogy expert and was not comparing the two tests as far as the accuracy of determining my ancestry.

Comparing 23andMe and AncestryDNA tests:

Taking the test:

Both companies are fairly similar in the simplicity of getting the testing done. You order the kit — either through the company websites or other online vendors— and it comes in the mail. The box contains a vial to spit into, instructions on how to register the kit, and a small pre-paid shipping box to mail the vial back to the company.

Both 23andMe and Ancestry.com advertise that it takes 4 – 6 weeks to get the test results back after they receive your vial of spit. It was faster than advertised (about 2 weeks for AncestryDNA) when I did the tests, but I think the times can vary depending on how busy the lab is when you send in your test.

The privacy policies:

Privacy policies: 23andMe.com Privacy Policy, AncestryDNA Privacy Policy

Read the terms of service and the full privacy policy. Make sure you understand and are ok with them before you order your kit.  Understand how both companies are using your genetic data.

Once you have taken the test, you also have the option of answering research “survey” questions on 23andMe and on Ancestry.com. Be sure that you understand that you are giving your survey information to the companies to use for their own purposes.

Downloading the raw data:

Both companies allow you to download and keep your raw data file. I highly recommend that you do so as soon as you get the results. The information is yours, and you should keep it safe.
Here are directions on how to download the raw data:
Download your genetic data from 23andMe.com
Download your genetic data from AncestryDNA

Both companies also have a clearly stated way to delete your data from their records if you choose to close your account with them. Here are the directions: Deleting your 23andMe account; for AncestryDNA, there is a button to delete data right under the download link on your settings page.

Searching your raw data online:

23andMe.com has a convenient interface for searching through your raw data on its website. It is in their Tools section, under Raw Data. You can search by rs id number or by gene name. AncestryDNA does not seem to have this option.

Using your raw data file:

The raw data file for both companies comes as a zipped text file.  Both files include the rs id #, chromosome, position, and your genotype. AncestryDNA’s data is formatted a little bit differently in that the genotype is given separately as “allele 1” and “allele 2”, where 23andMe combines the information into a “genotype” column.

You can simply open up the text file on your computer and do a “Find” to search for an rs id number. Everyone should have the ability to open a text file on their computer, no matter the operating system.

A better option (in my opinion) is to import the text file into Excel. To do so, open a new Excel Workbook and click on the Data tab. There should be an icon labeled “Text” that lets you import a text file. Both the 23andMe and AncestryDNA files are tab-delimited. Simply accept all of the default settings in Excel for the text import.

Importing it into Excel then gives you the option of using a second worksheet to make notes on what you learn from your genetic data.

23andMe raw data imported into Excel.

How accurate is the 23andMe or AncestryDNA raw data?

This is a harder question to answer. One way to look at the accuracy is to compare the data for the same person between the two files, which I’ve done below.  Important to note here is that 23andMe has proven accuracy to the FDA on a number of rare mutations, which they include in their health reports. Essentially, they are double-checking the data for certain mutations to make sure it is accurate.

Comparing the raw data files:

I decided to compare my 23andMe (v. 4) data file with the AncestryDNA file. 23andMe gives data for over 600,000 nucleotide base pairs, and AncestryDNA’s raw data covers over 650,00 base pairs. Comparing the two files, there were over 303,000 rs ids in common between the two. (This isn’t a completely accurate comparison since 23andMe reports some of the chromosome positions in a proprietary i-number format instead of as an rs id, but it is close enough for my purposes.)

Of the ~303,000 rs id’s in common, for my data, there were just over 1,000 for which the genotypes did not match. This comes out to 0.3% that did not match — or, alternatively, 99.7% that did match.

Which test is more accurate?

Knowing that for my data the two data files matched for 99.7% of the data actually doesn’t tell me anything as far as which one is ‘correct’ for the ~1,000 genotypes that differed.  Neither company guarantees that their testing is accurate, and both companies are very up-front about it with disclaimers stating that it isn’t being offered as a medical test.

I was actually expecting the mismatch percentage to be higher between the two tests.  While I’m not an expert on error rates in genetic sequencing, several studies that I had read lead me to expect that there would be more variation in the tests.

Final thoughts:

Everyone who is doing either AncestryDNA testing or 23andMe testing needs to read the privacy policies and also understand that the data shouldn’t be used as the only basis for making major medical decisions.

I’m fine with a tiny bit of uncertainty in looking at my genetic data for information about whether I should eat more foods that are high in choline or add in more leafy greens for folate.

Always double-check with a test ordered through a lab certified for that test before making any major health decisions.

What can you do with the raw data files?

While the data from 23andMe or AncestryDNA doesn’t cover everything, you can still learn a lot about optimizing your health!  The variants in the raw data files were chosen to cover most of the major genetic variants of interest, both for health and for ancestry.

Genetic Lifehacks has a ton of free articles on using your genetic data:

Interesting and fun articles to get you started:

Want more serious information, such as avoiding heart attacks and other major genetic risks? Check out the Top 10 Genes to Check In Your Genetic Data.

 

Genetic Lifehacks also has a membership option that makes it easier to see your genetic data. The membership also includes topic summary reports to give you an overview of articles that apply to your genes. I encourage you to check out some of the free articles first to see what this website is all about. If you love it, then sign up for a membership!

 



Author Information:   Debbie Moon
Debbie Moon is the founder of Genetic Lifehacks. She holds a Master of Science in Biological Sciences from Clemson University and an undergraduate degree in engineering from Colorado School of Mines. Debbie is a science communicator who is passionate about explaining evidence-based health information. Her goal with Genetic Lifehacks is to bridge the gap between the research hidden in scientific journals and everyone's ability to use that information. To contact Debbie, visit the contact page.