23 and Me vs Ancestry: Accuracy

Wondering how accurate your data is from 23andMe? Trying to decide between Ancestry.com or 23 and Me? I recently picked up an AncestryDNA kit to find out how well the raw 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 regarding the accuracy of determining my ancestry composition. Instead, I am exploring how the two tests match up for genetic accuracy.

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 through company websites or other online vendors, and it comes in the mail. The box contains a vial to spit into, instructions on registering 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:

Read the terms of service and the full privacy policy. Ensure you understand and are ok with the policies before ordering 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 23 and Me and on Ancestry.com. Be sure that you understand that you are giving your survey information to the companies to use for their purposes.

Downloading the raw data:

Both companies allow you to download and keep your raw data file. I highly recommend doing 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:

Both companies have a clearly stated way to delete your data from their records if you 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 have this option. Instead, you’ll need to download and then search through the raw data file.

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”, whereas 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 23 and Me and AncestryDNA files are tab-delimited. Simply accept all of the default settings in Excel for the text import.

Importing it into Excel then allows you to use a second worksheet to make notes on what you learn from your genetic data.

How accurate is the 23 and Me raw data vs the AncestryDNA raw data?

This question is harder 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 double-check the data for certain mutations to ensure it is accurate.

Comparing the raw data files:

I decided to compare my 23andMe (version 4) data file with the AncestryDNA v2 raw data file.

23andMe gives data for just 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.

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. It 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.

Neither company guarantees that their testing is clinically accurate, and both companies are very up-front about it, with disclaimers stating that it isn’t being offered as a medical test.

One thing to consider, though, is that 23andMe has FDA approval for reporting on a number of genetic mutations. It means that their genetic sequencing has gone through accuracy checks for those specific mutations that they include in their health reports.

On my data, the mismatches that I spot-checked using my parents’ raw data showed that 23andMe was more likely to be correct.

Final thoughts:

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 led me to expect that there would be more variation in the tests.

Everyone doing either AncestryDNA testing or 23 and Me testing needs to read the privacy policies and 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 23 and Me 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 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.

Membership makes it easier!

Genetic Lifehacks offers 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 free articles first to see what this website is all about. If you love it, then sign up for a membership!