December 16, 2020

A Genetic Test You Don’t Need

Testing MTHFR is usually unnecessary

preforming genetic testing in the lab

By: Charis Eng, MD, Ph.D


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As a geneticist and researcher, I believe in the power of genetic testing. By identifying genetic mutations, we can improve care and save lives.

But just because we can test something doesn’t always mean we should.

Take the MTHFR gene, for example. MTHFR codes for an enzyme that helps your body convert homocysteine into an amino acid that processes proteins. People with homozygous (present in two copies) mutations or variations of MTHFR may end up with homocystinuria, a disorder that affects the eyes, joints and other parts of the body. High homocysteine levels also have been connected to heart disease and strokes.

There is a genetic test for MTHFR variations. But there’s also a cheaper and more accurate way to test for whether MTHFR variations are causing disease. We simply check the levels of homocysteine in the blood. If levels are high, we can react appropriately. If homocysteine levels are normal — even if there is an MTHFR variation — then nothing needs to be done clinically.


In other words, the homocysteine levels determine our actions, not the MTHFR test results.

Simple test, simple solutions

Not only is the test for homocysteine levels simple, but so are the solutions. People with high homocysteine levels typically respond well to supplementation with vitamins such as B6, B12, and folate or folic acid.

The same is true of other disorders that might be related to MTHFR. For example, mutations in MTHFR have been associated with some neural tube defects in babies. But rather than having an unnecessary test for MTHFR gene variations, pregnant people should simply take prenatal vitamins that contain higher folate.

Folate effectively bypasses the problem — and it’s benign at the doses that come in vitamins.


Keeping care accountable

Variations of MTHFR have been studied in connection to stroke, high blood pressure and heart disease, as well as bipolar disorder and other conditions. But the associations have not been established as clear-cut. Until they are, most geneticists — myself included — feel a test for MTHFR is not necessary in the vast majority of cases.

In an era when affordable, accountable care is crucial, keeping an eye on which tests truly improve care and which ones may waste money is more important than ever.

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