Evidence Lacking for Widespread Vitamin D Deficiency Screening

Update: The U.S. Preventive Services Task Force finalized these recommendations on April 13, 2021. 

The U.S. Preventive Services Task Force (USPSTF) has declined to make a recommendation for or against screening for vitamin D deficiency in the general population in their latest statement.

The expert group’s September 22, 2020 draft recommendation continues its 2014 stance: Current research does not provide enough evidence to evaluate whether screening for vitamin D deficiency in asymptomatic adults would be beneficial. Because evidence is lacking, the Task Force refrained from making a recommendation for or against screening. The recent draft recommendation does not apply to people who have risk factors for vitamin D deficiency and/or health conditions that require vitamin D supplementation. Groups at higher risk of deficiency include the elderly, people with obesity or who don’t get enough sunlight exposure, people with darker skin, and those who take certain medications (e.g., phenytoin, prednisone, statins) for long periods of time.

Vitamin D is a fat-soluble vitamin that plays an important role in the growth and health of bones and teeth. It is produced in the skin during sunlight exposure and obtained through the diet and supplements.

According to an analysis of 2011-2014 National Health and Nutrition Examination Survey data, most of the U.S. population have sufficient vitamin D, while 18% are at risk of inadequate vitamin D (levels of 30 to 49 nmol/L or 12 to 19.6 ng/mL). About 5% of the population are at risk of vitamin D deficiency (levels less than 30 nmol/L or 12 ng/mL), which is associated with osteoporosis, increased risk of falls, and bone fractures.

Healthcare practitioners often order vitamin D tests. While lab tests can measure different forms of vitamin D in the blood, the 25-hydroxyvitamin D blood test is typically used to assess vitamin D status. However, accurately measuring 25-hydroxy vitamin D is difficult, according to the USPSTF. Results can vary depending on the method used as well as between labs using the same method. Additionally, not enough evidence shows whether screening for and treatment of asymptomatic low 25-hydroxyvitamin D levels improves health outcomes. Vitamin D requirements vary from person to person, so there is no single level of vitamin D that is considered too low for everyone, the USPSTF added.

The draft recommendation warns that screening may misclassify people with a vitamin D deficiency because of the uncertainty about the threshold for defining deficiency and the variability of available tests. Misclassification would result in people with healthy vitamin D levels getting unnecessary treatment or those who need vitamin supplementation not receiving it.

“Based on our review, the Task Force determined there is not enough evidence to recommend for or against screening for vitamin D deficiency in adults without signs or symptoms,” Task Force member Michael Silverstein, M.D., M.P.H. said. “We need more research to know what level of vitamin D people need to keep them healthy and what level is too low and can have negative health impacts.”

“Once we know the level of vitamin D that people need to remain healthy, or if there is a better test, more research on whether screening can help prevent negative outcomes, such as falls, cancer, or heart problems will be helpful,” added Task Force member John Wong, M.D.

No healthcare organization currently recommends population-based screening for vitamin D deficiency. The American Society for Clinical Pathology (ASCP) specifically recommends against it, while the Endocrine Society does not recommend screening for vitamin D deficiency in individuals not at risk. ASCP and the Choosing Wisely program advise that people who are concerned about low levels of vitamin D talk to their doctors about their risks.

Healthcare practitioners may order a vitamin D test for people who have osteoporosis or a disease that damages the body’s ability to use vitamin D, including pancreatitis, inflammatory bowel disease, celiac disease, kidney disease, or liver disease. Other diseases that interfere with fat absorption, like cystic fibrosis, may also prompt testing.

In individuals requiring repeated vitamin D tests, ASCP and Choosing Wisely recommend that patients have the tests done by the same method and laboratory each time.