Seven years after concluding that evidence was insufficient to recommend screening for vitamin D deficiency in the general population, the United States Preventive Services Task Force (USPSTF) has revisited the issue – and come up with the same conclusion.
Overall, “the current evidence is inadequate to determine whether screening for and treatment of asymptomatic low 25(OH)D levels improve clinical outcomes in community dwelling adults,” the task force concluded in its statement, recommending an “I” for insufficient.
The statement was published online April 13 in JAMA.
In the absence of screening recommendations, clinicians may be best advised to instead focus on diet and supplementation for those considered at risk, said Anne R. Cappola, MD, of the University of Pennsylvania, Philadelphia.
“Rather than posing the question of screening the general population for vitamin D deficiency, let’s focus on ensuring that everyone consumes the age-based recommended daily allowance of vitamin D instead,” Dr. Cappola, a coauthor of the accompanying editorial, said in an interview.
No studies have directly evaluated benefits of screening
The latest USPSTF recommendation is based on a systematic review of the benefits and harms of screening and early treatment for vitamin D deficiency in asymptomatic, community-dwelling nonpregnant adults aged 18 or older in the primary care setting with no signs or symptoms of deficiency.
The review found no studies that directly evaluated the benefits of screening for vitamin D deficiency.
However, 26 randomized clinical trials and one nested case-control study evaluated the effectiveness of treatment of vitamin D deficiency with supplementation.
And while observational studies have linked lower vitamin D levels with a multitude of conditions and risks, evidence of any benefit was inconsistent, with none identified for most major outcomes in asymptomatic adults – the focus of the Task Force recommendation.
“Among asymptomatic, community-dwelling populations with low vitamin D levels, the evidence suggests that treatment with vitamin D has no effect on mortality or the incidence of fractures, falls, depression, diabetes, cardiovascular disease, cancer, or adverse events,” the review authors stress.
“The evidence is inconclusive about the effect of treatment on physical functioning and infection.”
One in four are vitamin D deficient
In terms of the further question of the potential harms of vitamin D screening of asymptomatic individuals, a key concern is the potential for misclassification and over- or underdiagnosis due to inconsistent cutoffs and variability of different screening assays, the review concluded.
However, with the rare exception of vitamin D toxicity from supplementation well above sufficient levels, treatment with vitamin D supplementation appears relatively safe.
With a lack of consensus even over the basic cutoff for vitamin D deficiency, the National Academy of Medicine determined in 2011 that hydroxyvitamin D (25[OH]D) levels below 20 ng/mL are deficient for bone health, with no evidence of different thresholds for any other health condition.
Based on that cutoff, the National Health and Nutrition Examination Survey (NHANES), reported in 2014 that 25% of the U.S. population over the age of 1 was vitamin D deficient, with 18% of the population having 25(OH)D levels of 12-19 ng/mL and 5% having very low levels (< 12 ng/mL).