At-home microbiome tests show dramatically different results

Researchers gave the same sample to seven home microbiome tests. The results were dramatically different

By KR Callaway edited by Claire Cameron

From drinking celery juice to drinking supplements to eating fistfuls of probiotic-rich foods like kimchi, gut health is high on the wellness agenda. And while you’re trying to help your own good bacteria flourish, at-home testing companies are also booming that claim to open the black box of digestive health.

It’s easy to understand why we’ve become so obsessed with our stomachs. Scientists have long known that huge colonies of bacteria, viruses and other microorganisms – a population collectively known as the microbiome – live on and inside the human body. But how they affected our health was a mystery for a long time. Over the past few years, we’ve learned that countless factors, from the food we eat to the amount of time we spend sleeping to our genes to our home, all influence our microbiome. And in turn, it can affect our immunity, digestion and aging and even our emotions.

And that’s why home microbiome testing has blossomed into a more than billion-dollar market. But a study published today in Communication biology suggests that some of these tests’ insights may not be as accurate as they claim.

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“The gut microbiome has been linked, at least in the public imagination, to the idea that you can improve a whole range of conditions through diet and lifestyle change,” says Diane Hoffman, co-author of the study and professor of health law at the University of Maryland, Baltimore. “There’s been a lot of hype around it, but the hype doesn’t match the evidence.”

According to Hoffman and her co-authors, home microbiome tests “cut across the line” between medical and wellness products, placing them in a legal gray area. Currently, there are no microbiome diagnostic tests approved by the Food and Drug Administration for clinical use in the United States, although the market for at-home versions continues to grow.

These direct-to-consumer microbiome tests rely on the user to collect their own stool samples at home — essentially scooping their own stool into a vial and sending it to a lab for analysis. Stool samples are an effective way to find out which microbes are present in the digestive tract. But different parts of the sample and different ways of storing or processing it can give dramatically different results. To get a clear idea of ​​how capable the home tests were, Hoffman and her team created a sample stool sample by mixing healthy stool until the mix of organisms was homogeneous throughout.

The research team then randomly selected seven different companies – none of which are named in the study – and collected samples from the same initial fecal source, following the companies’ collection methodology. The team completed and sent back three separate tests to each of the companies. This enabled the researchers to compare the different companies’ results – and test whether each company’s analysis was precise enough to show similar results from all three versions of the sample.

The results were even more different than the team had expected. Of the more than 1,200 taxonomic groups of microbes identified by all the tests combined, only three microbial genera were present in all seven companies’ results. Even tests processed by the same company did not always agree.

In one case, a company sent back the results of its three separate tests with two labeling that version of the sample “healthy” and one labeling it “unhealthy.” Such discrepant results make the test’s uncertainties unmistakable, says Scott Jackson, co-author of the study and former employee of the National Institute of Standards and Technology. “You can see it stands out like a sore thumb.”

The researchers caution that people using these direct-to-consumer tests should not use the results to inform lifestyle changes or medical decisions — especially until the analyzes are potentially supported by more research and regulation.

“It’s still relatively early as a scientific field,” says Jackson. “I think we’ll find out, but we’re just not there yet.”

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