Common Misleading Tests: Thyroid and Troponin

Dr. Stacey Clardy reviews biotin deficiency and biotin-related lab interference.

Show transcript:

Dr. Stacey Clardy:

Hi, this is Stacey Clardy from the Salt Lake City VA and the University of Utah, and I'm back with you for another lab minute. Today, let's talk about Biotin or vitamin B7, because the Biotin story in neurology has two very different aspects. The first is a real deficiency, which is uncommon, but clinically really important. And the second is the modern problem of biotin supplementation that's quietly wrecking our lab interpretation.

So first, true biotin deficiency in adults is less common, but it can look like a multi-system neurologic syndrome. The classic teaching is dermatitis and alopecia, so keep those in your mind. But neurologists end up seeing the downstream features. So lethargy, depression, paresthesias and sometimes ataxia. Now, in infants and children, the bigger higher stakes entity is biotinidase deficiency, which is fortunately screened in many newborn programs in the US. Untreated, it can produce seizures, developmental delay, optic atrophy, and hearing loss. And the key point is that these neurologic injuries can be prevented if biotin is started early enough.

Also, remember, there are numerous reports now in the literature of it mimicking the clinical and radiological features of neuromyelitis optica spectrum disorder or multiple sclerosis. So if you have one of those diagnoses and you're not quite sure that it's right, keep biotinidase deficiency in the back of your mind. Now, what most of us clinicians are living with is the biotin supplement era. So high dose biotin, taken by a lot of people, either knowingly or unknowingly, can interfere with biotin streptavidin immunoassay platforms. And the direction of error depends on the assay design, but the practical pitfalls are simple. You can be handed a lab pattern that screams something like hyperthyroidism or other endocrine pathology, and it can actually be purely analytical artifact. Thyroid testing is the most common example, and troponin and other assays can also be affected depending on the assay platform.

So a common clinical misstep is to treat the lab burnout rather than the patient. So if your patient symptoms don't match this new endocrine emergency that the lab appears to be showing, ask, are they taking biotin? This is commonly in hair and nail supplements or buried in the myriad ingredients of another fix all supplement. So you need to find out if it's in any of those. The easiest thing is to say, tell me all of the supplements and the brands you're taking. And then I usually do a quick internet search right there to find out if biotin's in there.

And so the lowest friction fix is generally to repeat the test after holding biotin for an appropriate interval. At least a week is usually a safe time to guess about. The key is coordination with the laboratory. Not every lab behaves the same and some systems now actually have evolved mitigations, which is quite helpful. So that's the biotin update. So remember, biotin deficiency is treatable and sometimes urgent. And also, biotin supplementation is now a common lab confounder that can trigger avoidable diagnostic and therapeutic errors. Thanks for spending a few minutes with me. This is Stacey Clardy, and that's your lab minute.