Now that I have my new shiny “Numbers Aren’t Magic” tag, I thought I’d use it for a bit of a PSA. I’m on a lot of laboratory testing related email lists for work, and I recently got a notification from the College of American Pathologists with a rather intriguing headline “Beauty Fad’s Ugly Downside: Test Interference“.

The story was about biotin (also called Vitamin H) a supplement widely touted as a beauty aid because it (allegedly) makes your hair and nails look better (example here). Unfortunately, it turns out that quite a few widely used immunoassays actually use biotin  to capture their target antibodies during testing, and unusually high levels in the blood interfere with this. In other words, high doses of biotin in your supplement could interfere with your lab results. Uh oh.

The news of this first broke in January, when it was discovered that some patients were getting bad thyroid test results that had resulted in an incorrect diagnosis of Graves’ disease. Since then, the awareness among endocrinologists has grown, but there’s concern that other potentially affected tests are being missed. Apparently cardiac markers, HIV and HCV tests could also be affected.

The problem here is really megadoses. These assays were designed to work with normal blood levels of biotin. The recommended daily amount is only 30 micrograms, but supplements like the one I linked to above actually give doses of 5000 micrograms….166 times higher, and in to the range of test interference. You only have to stop taking it for a day or two before the interference issues go away, but most people and doctors don’t know this.

I’m bringing this up for two reasons:

1. I didn’t know it, and I think more people should be aware of this.
2. It’s a good reminder that almost every number ever generated is based on a certain set of assumptions that you may or may not be aware of.

Numbers don’t often spring out of the head of Zeus fully formed, they are almost always assessed and gathered in ways that have vulnerabilities. For anyone attempting to make sense of those numbers, recognizing vulnerabilities is critical. If even lab tests (some of the most highly regulated medical products we have) can have issues like this, imagine what numbers with less stringent requirements could fall prey to.

PS: I couldn’t find biotin on the Information is Beautiful Supplement Visualization, but here’s the link anyway because it’s still pretty cool.