The U.S. Preventive Services Task Force made no recommendation for or against primary care physicians screening asymptomatic adults for vitamin D deficiency, because the current evidence is insufficient to adequately assess the benefits and harms of doing so, according to a report published online Nov. 24 in Annals of Internal Medicine.
The USPSTF reviewed the evidence on screening and treatment for vitamin D deficiency, because the condition may contribute to fractures, falls, functional limitations, cancer, diabetes, cardiovascular disease, depression, and excess mortality.
In addition, testing of vitamin D levels has increased markedly in recent years. One national survey showed the annual rate of outpatient visits with a diagnosis code for vitamin D deficiency more than tripled between 2008 and 2010, and a 2009 survey of clinical laboratories reported that the testing increased by at least half in the space of just 1 year, said Dr. Michael L. LeFevre, chair of the task force and professor of family medicine at the University of Missouri, Columbia, and his associates.
Dr. Michael L. LeFevre
The organization is a voluntary expert group tasked with making recommendations about specific preventive care services, devices, and medications for asymptomatic people, with a view to improving Americans’ general health.
The task force reviewed the evidence presented in 16 randomized trials, as well as nested case-control studies using data from the Women’s Health Initiative. They found that no study has directly examined the effects of vitamin D screening, compared with no screening, on clinical outcomes. There isn’t even any consensus about what constitutes vitamin D deficiency, or what the optimal circulating level of 25-hydroxyvitamin D is.
Many testing methods are available, including competitive protein binding, immunoassay, high-performance liquid chromatography, and mass spectrometry. But the sensitivity and specificity of these tests remains unknown, because there is no internationally recognized reference standard. Moreover, the USPSTF found that test results vary not just by which test is used, but even between laboratories using the same test.
Symptomatic vitamin D deficiency is known to affect health adversely, as is asymptomatic vitamin D deficiency in certain patient populations. But the evidence that deficiency contributes to adverse health outcomes in asymptomatic adults is inadequate. The evidence that screening for such deficiency and treating “low” vitamin D levels prevents adverse outcomes or simply improves general health also is inadequate, Dr. LeFevre and his associates said.
Similarly, no studies to date have directly examined possible harms of screening for and treating vitamin D deficiency. Although there are concerns that vitamin D supplements may lead to hypercalcemia, kidney stones, or gastrointestinal symptoms, there is no evidence of such effects in the asymptomatic patient population.
The USPSTF concluded that the harms of screening for and treating vitamin D deficiency are likely “small to none,” but it still is not possible to determine whether the benefits outweigh even that small amount of harm.
At present, no national primary care professional organization recommends screening of the general adult population for vitamin D deficiency. The American Academy of Family Physicians, the Endocrine Society, the American College of Obstetricians and Gynecologists, the American Geriatrics Society, and the National Osteoporosis Foundation all recommend screening for patients at risk for fractures or falls only. The Institute of Medicine has no formal guidelines regarding vitamin D screening, Dr. LeFevre and his associates noted.
The USPSTF summary report and the review of the evidence are available at www.uspreventiveservicestaskforce.org.