CAP TODAY Pathology/Laboratory Medicine/Laboratory Management
Dr. Wright
“Biotin is a known interference that has been quantified for the last 20 years, and for 20 years we’ve had our immunoassay package inserts call out that patients should not take large doses of biotin for eight hours before a sample is collected,” says Alan Wright, MD, chief medical officer of Roche Diagnostics. “Biotin is just now becoming more visible to the laboratory community because of this new trend of taking high-dose biotin.”
Because megadoses of biotin are catching on as health improvement aids, Roche is actively conducting studies to determine two things: the pharmacokinetics, or how biotin is metabolized, and the prevalence of megadose biotin therapy.
“Interference has been with laboratory medicine since we started doing lab tests,” Dr. Wright says. “All the way from hemolysis and potassium measurements in the blood, which would be preanalytic interferences, or high lipids in bloods which can interfere, to medical conditions like lupus that lead to anticoagulants which can interfere with blood clotting tests. And there are also conditions that include the presence of anti-thyroid thyroglobulin which can interfere with thyroid tests. So it’s important for a laboratorian to be able to consult with clinicians and be able to explain the potential interference of any assay.”
Many diagnostics manufacturers use the biotin-streptavidin system for many assays, he confirms. “The biotin-streptavidin system is a very robust platform to bind an antibody. You have an antibody which looks like a ‘Y,’ with biotin at the base of the Y, then you have it bind to streptavidin, and that is a common technique. I would say it’s very prevalent throughout the diagnostics industry,” Dr. Wright says.
The use of megavitamins is not new, he notes, pointing out that people have consumed vitamin C in large amounts for decades. “Right now the megavitamin is biotin. We are aware of this trend and interested in understanding more about it. We’re working with our lab customers to talk with them about biotin interference.”
Whether patients are aware they are taking biotin is part of what Roche is studying. “But one of the things about this interference is you can’t get these high levels of biotin by consuming an over-the-counter multivitamin. That is not an issue. You have to specifically consume a product that is made to have super-pharmacologic doses of biotin.” At this stage, estimating patient awareness involves supposition, Dr. Wright says. “But I would think somebody who seeks out a high-dose preparation would know they are taking a high dosage of biotin.”
Freeman
There’s no dispute that biotin, when taken in megadoses as a supplement, can cause interference in immunoassays that use a biotin-streptavidin architecture, says James Freeman, senior director of immunoassay development for Siemens Healthcare Diagnostics. However, he says there are differences among manufacturers in how the technologies are applied to the assays.
“The architecture of an immunoassay dictates whether an interference with biotin is observed. Heterogeneous immunoassays use a solid phase to capture the desired analyte. Several manufacturers use streptavidin immobilized on the solid phase and a biotinylated antibody to capture the analyte,” Freeman says, adding that the Advia Centaur systems use this streptavidin-biotin assay format in about one quarter of Siemens’ commercialized immunoassays. “But the biotin-streptavidin assay architecture can be either a preformed biotin-streptavidin solid phase or a non-preformed such phase. Biotin interference is typically observed only when you have a non-preformed biotin-streptavidin solid phase.”
Siemens’ immunoassays primarily use preformed solid phase, Freeman says. “Approximately six of the Siemens immunoassays on the Advia Centaur systems, which has over 75 assays available, demonstrate some level of biotin interference. We publish the level of interference in our Instructions for Use.” None of Siemens’ other immunoassay platforms demonstrates a biotin interference, to his knowledge.
Siemens is proactively conducting research to determine the extent and gravity of potential biotin interference, Freeman says. “When we use a biotin-streptavidin assay architecture, we use an experimental design to determine the exact level of biotin that would cause interference, and we publish that in our Instructions for Use.”
While biotin interference in immunoassays has been known for decades, he adds, it was not considered a serious obstacle because biotin was not used as extensively as it is today.
Now that taking megadoses of biotin has become more prevalent, there could be a lot of turmoil as manufacturers whose products have more sensitivity to biotin try to respond, Freeman predicts. “Patients taking high doses of biotin could experience ramifications with some assays. Depending on the assay manufacturer, you can have an infectious disease assay such as an HIV or HCV test where an individual is misdiagnosed.” The Siemens HCV and CHIV assays use a preformed streptavidin solid phase. “Therefore, biotin interference is not observed with these assays,” he says. “Or, for example, if I have chest pain and go to the emergency room, I could have elevated or suppressed troponin results depending on whether I took biotin or not and which assay is used to measure the troponin levels. So those are serious clinical cases where there might be a misdiagnosis.”
Biotin happens to be useful technology for immunoassays because the biotin-streptavidin interaction has one of the highest binding constants that is known, Freeman says. “In other words, streptavidin and biotin combine very strongly and very quickly. They have a well-documented binding event that is very strong and fast, and that’s typically why manufacturers use biotin and streptavidin in immunoassay architecture.”
Freeman says it’s important for labs to understand the knowledge gap that surrounds biotin interference. “Five or 10 years ago, the only individuals who demonstrated this interference were undergoing dialysis, and doctors knew the patients were undergoing dialysis and knew they had biotin levels that might interfere, based on manufacturers’ instructions for use. Today, with people taking more and more of these supplements, the doctors don’t know and labs don’t know, unless they actually test for biotin.”
Roche always evaluates ways to remove or reduce possible interferences, including biotin, and provides clear test labeling to ensure physicians and laboratories can mitigate risk where there is interference potential, Dr. Wright says. Roche advises labs to carefully review assays’ package inserts, which fully reference biotin interference as a risk. “I’m in charge of medical and scientific affairs, and when we get inquiries about this, we refer labs back to the package insert and we have interim studies that we refer to as well,” he says. “We also work with outside labs and use our customer base to develop question-and-answer materials and conduct peer-to-peer consultation regarding the biotin issue.”
Of about 628 million thyroid tests a year supplied by Roche, Roche has had 14 biotin-related case reports so far. “So it’s important to us, but it’s important to understand the magnitude of case reports versus how many thyroid tests we do per year. We think that our assays are very high quality, very sensitive and specific.”
“In any forward-thinking analytics company—Roche and our competitors included—we always try to improve what we’re doing. In biochemistry we’re always looking for new ways to do these tests, and on an emergent basis, we’re going to continue investing to improve assay design,” Dr. Wright says.
For its part, LabCorp is hoping to increase clinician >knowledge of biotin interference and has reached out to the manufacturers to see how they are addressing the problem, Dr. Valcour says. “We are being proactive to get the issue out in the forefront. In fact, as an organization we are looking at every single test we offer to see which have exposure to this interference.” But LabCorp’s inquiry is at an early phase.
What can laboratories do? While some steps have been proposed, it’s too soon to recommend measures such as posting signs in phlebotomy units asking patients whether they are taking biotin, Dr. Valcour believes. “I would say getting clinicians to know whether patients are on biotin and to tell patients to stay off biotin before testing is probably the most efficient and most efficacious approach to preventing interference. This would help in two ways. First, it makes physicians aware of supplementation and what their patients are taking, and, second, it makes them aware, when looking at lab results, that interference is a possibility.”
An alternative would be for labs to ask at the point of collection whether the patient is taking biotin. But patients may not know when they took their last dose or exactly what they took, if they know the biotin as vitamin H or by some other name. “That puts the doctor in a very precarious position, because even if the result is perfectly normal and consistent with clinical expectations, it’s very hard to trust that result if the patient might have been taking biotin,” Dr. Valcour says. “We would have to stop them from taking biotin a day, or I would say at least two days, before they show up to be drawn—and the only one who can really do that would be the clinician.”
Laboratories should, however, push for further investigation of biotin interference, Dr. Valcour says. “At this point, working with the diagnostic manufacturers to try to understand the extent to which our assays are affected by biotin, and down the road, the effect of various disease states on clearance, would be something that laboratories should help with.”
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Anne Paxton is a writer and attorney in Seattle.