Still No Consensus on the Need for Vitamin D Deficiency Testing

Evidence for-or against-vitamin D testing is still “insufficient,” the U.S. Preventive Services Task Force said last week.

Opinions still vary on the value of widespread vitamin D deficiency testing. Just last week, the U.S. Preventive Services Task Force (USPSTF) said in a draft recommendation that “current evidence is insufficient to assess the balance of benefits and harms of screening for vitamin D deficiency.”

Vitamin D testing is on USPSTF’s radar because both testing and sales of vitamin D products have skyrocketed in recent years. According to USPSTF, “data from the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey found that the annual rate of visits associated with a diagnosis code for vitamin D deficiency more than tripled between 2008 to 2010…” Moreover, in a 2009 survey of clinical laboratories, more than half of the laboratories reported that “total serum 25-hydroxy vitamin D testing increased by at least 50% compared with the previous year.”

The benefits of vitamin D deficiency testing, as well as the population’s overall vitamin D status, are still unknown for one important reason: because it’s still uncertain what the ideal vitamin D level should be, USPSTF said.

There is no agreed-upon definition for vitamin D deficiency or what the optimal level of serum 25-hydroxy vitamin D should be. USPSTF said the cutpoint often ranges between 20-30 ng/ML. Moreover, vitamin D levels can vary depending on ethnicity (e.g., lower in the black and Hispanic populations), as well as lifestyle influencers such as exposure to sunlight, smoking, obesity, and poor diet-making a standardized measurement and target difficult to pinpoint.

Current vitamin D deficiency test methods are also not standardized, USPSTF pointed out. Today’s methods range from competitive protein binding to immunoassay, high-pressure liquid chromatography (HPLC), and combined HPLC and mass spectrometry (LC-MS/MS), all of which can yield different results. “The USPSTF found evidence suggesting variation in results between testing methods and between laboratories using the same testing methods,” USPSTF said.

“In order to collect precise estimates, accurate assay methods, an internationally recognized reference standard, and a cutpoint for defining vitamin D deficiency need to be established,” USPSTF said, otherwise we run the risk of under-diagnosing or over-diagnosing patients.

USPSTF is now seeking comments on its draft recommendation statement until July 21, 2014.

Vitamin D’s current high profile is due to more studies linking low vitamin D levels to chronic conditions such as bone health, cognitive impairment, heart disease, and cancer. National Health and Nutrition Examination Survey (NHANES) data from 2005-2006 estimated vitamin D deficiency in the overall U.S. population is 42%, with higher deficiency rates in the black and Hispanic populations.

Critics, including the authors of a recent British Medical Journal editorial, argue that media hype over vitamin D may lead some consumers to erroneously believe that this nutrient is a “panacea” for chronic disease. The BMJ authors recommend against routine vitamin D testing until mores studies are available to prove vitamin D’s benefits. “[W]hile we wait for results of major trials, clinicians should avoid costly measurement of 25-hydroxyvitamin D in asymptomatic patients outside of bone disease related conditions.”

But one of Nutritional Outlook’s authors argues that although vitamin D may not be a panacea for chronic disease, it is still an important nutrient and should be viewed as such.

Although widespread testing is not yet recommended, individuals can still choose to get tested. Customer service representatives at both Anthem Blue Cross and Kaiser Permanente told Nutritional Outlook that preventive testing like vitamin D testing is covered if a healthcare provider deems it medically necessary.

 

Jennifer Grebow
Editor-in-Chief
Nutritional Outlook magazine
jennifer.grebow@ubm.com