New measurement standard for vitamin D may lead to better bone health

In a development that could help improve the prevention and treatment of osteoporosis, rickets and other bone diseases, government chemists are reporting progress developing an accurate, reliable set of standards for measuring vitamin D levels in blood.

Their findings could affect the health of millions of people worldwide, particularly children, women and the elderly who suffer from or are at risk of these debilitating diseases, according to a press release.

The researchers presented their findings this week at the American Chemical Society’s 237th National Meeting.

The advance comes in the midst of a growing awareness that many children and adults are not getting enough vitamin D. New studies also link vitamin D deficiency to a higher risk of diseases ranging from osteoporosis to cancer to cognitive impairment in the elderly.

Despite concerns about adequate vitamin D intake, there is no standard laboratory test for measuring vitamin D levels in humans, and no universal agreement on what are considered “normal” or “optimal” vitamin D levels, according to the press release.

“No one really knows what methods or assays are correct at this point,” Mary Bedner, PhD, an analytical chemist with the National Institute of Standards and Technology (NIST) in Gaithersburg, Md., said in the press release. “Right now, you can send a blood sample to two different labs and get completely different results for vitamin D.”

About 3 years ago, NIST began developing a standard for measuring vitamin D in collaboration with the National Institutes of Health’s (NIH's) Office of Dietary Supplements. Later this year, NIST scientists plan to unveil their new standard to the public.

The most commonly used indicator of a person's vitamin D status is the measurement of 25-hydroxyvitamin D in the blood. But several different forms of this vitamin exist in the blood — including 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 — that are of clinical significance and could be overlooked by scientists focusing on total 25-hydroxyvitamin D alone.

To account for these other forms of vitamin D, NIST developed Standard Reference Material 972. The material is composed of four different pools of human blood serum obtained from a wide cross-section of blood donors. Each of the four pools contains different amounts of 25-hydroxyvitamin D2 and D3 to represent vitamin D profiles normally seen in a clinical setting. All were carefully measured using a combination of state-of-the-art liquid chromatography and mass spectroscopy, Bedner said in the press release.

By using these four blood samples as reference points, clinical laboratories can calibrate their instruments and measurement techniques to assure more accurate and reliable vitamin D measurements for blood samples. This would ultimately help physicians make the best treatment decisions, she said.

“Accuracy is key,” Bedner said in the press release. “We need to provide a reference material that other people can trust.”

The researchers plan to make their reference standard commercially available within the next year, according to the press release.