Vitamin-D testing benefits doubtful

Scimex: Two Australian experts say there's a danger that over-testing for vitamin D deficiencies may lead to lots of people with low vitamin D levels receiving unnecessary treatment. The researchers say that recent studies suggest there's no clear evidence for the benefits of vitamin D, so testing patients may be completely unnecessary. Over-testing for vitamin D deficiencies may lead to a sizable group of patients with low vitamin D levels receiving unnecessary treatment without clear evidence of benefit, including unneeded repeat testing, according to a Perspective published in the Medical Journal of Australia.

Controversies remain about who should be tested and who should be treated for vitamin D deficiency, wrote Dr Paul Glendenning from Royal Perth Hospital and Dr Gerard Tse-Jiun Chew from the University of Western Australia.

"The correction of vitamin D deficiency and assurance of adequate calcium intake have been cornerstones of osteoporosis management", they wrote.

However, a recent meta-analysis of clinical trials concluded that "vitamin D supplementation alone did not reduce total or hip fracture risk, but co-supplementation with vitamin D and calcium did".

Even more controversial is the role of vitamin D in extraskeletal diseases such as cancer, atherosclerosis,diabetes, infections and neurodegenerative diseases, with evidence clouded by possible methodological biases and confounding.

"Current evidence suggests that the main beneficial effects of vitamin D supplementation relate to musculoskeletal, rather than extraskeletal, health outcomes, with the subset of frail older patients with the highest likelihood of vitamin D deficiency being those most likely to benefit", Glendenning and Chew wrote.

Despite these controversies, there has a been a 94-fold increase in vitamin D testing between 2000 and 2010 in Australia, with repeat testing accounting for nearly half the test numbers, "despite only a 0.5-fold increase in bone mineral density testing over the same period".

Guidelines for vitamin D testing from the Royal College of Pathologists of Australasia (RCPA), released in 2013, specify that "the routine screening of healthy adults is not recommended, with the caution that doing so might reveal a significantly sizeable group with low vitamin D levels that could lead to treatment without clear evidence of benefit and perpetuate unnecessary repeat testing". Additionally, repeat testing should occur no earlier than 3 months after the start of supplementation or change in dose.

Glendenning and Chew suggested education initiatives to "increase general awareness and appreciation of the current evidence and guidelines for appropriate testing and supplementation", followed by an audit of local practice.