A new report reveals that several biotech companies are now selling "microbiome screening tests" through doctor’s offices in the U.S. and Europe.

This month’s issue of Nature Biotechnology explains that at least some of these tests are covered by health insurance. But should you consider having one? Here’s a quick rundown of how the screenings work, what they purport to measure, and whether or not they make sense for consumers.

What Is the Microbiome?

The microbiome is just the natural ecosystem of bacteria and other microorganisms that colonize the human body, mostly on the surface of the skin and throughout the gastrointestinal system.

These bugs begin making a home in you the moment you're born. In fact, scientists believe that the microbes that latch onto you as you pass through the birth canal may be so important to your health later on that they've been looking into whether—and how—those microbes could be given to babies born via C-section.   

Research has linked the microbiome to a growing list of conditions, including obesity, Parkinson's disease, and depression.

Scientists have been especially interested in issues related to the GI-tract, because that's where a majority of our resident microbes live. 

How Do Doctors 'Test' It?

In short, it's by sequencing the genes of the bacteria found in poop. Doctor take a fecal swab and send it to a testing company, which does the genetic analysis. 

That analysis tells them which bacteria are populating your gut. The company will compare your microbiome with a catalog containing tens to hundreds of thousands of other microbiomes in an effort to tell whether your gut contains specific microbes that have been linked to certain diseases and conditions. 

Most tests purport to test for irritable bowel syndrome; some also test for depression, rheumatoid arthritis, chronic fatigue and other ailments. 

Do These Tests Work?

The only fair answer at this point is that we don't know. Microbiome research has made impressive strides and promising developments in recent years. Scientists have identified hundreds of common intestinal microbes and have begun linking at least some of them to specific symptoms and conditions. 

But one of science's golden rules is that correlation doesn't equal causation. That is, showing that two things are linked isn't the same thing as proving that one caused the other. 

There's much more work to do before any doctor can say with confidence whether specific gut microbes are responsible for certain health outcomes—and whether it's the relative abundance of different bacterial species or the coexistence of some species with others, or even the absence of a certain species that tips a person toward illness. 

And if and when those connections are proved, healthcare practitioners will still face the same challenge that all doctors confront when treating intractable conditions: building from this new evidence of causation to get to actual treatments that are safe and effective for humans. 

Microbiome research is growing rapidly, so that day may come soon. But in the meantime, our experts say, it's probably best to skip the screening.