There is “inappropriate and unnecessary” testing of vitamin D levels being carried out in Dublin, according to researchers from Trinity College.
The researchers gathered and analysed data on repeat testing for vitamin D in a new study published in the Journal of Clinical Chemistry and Laboratory Medicine.
The study found “significant” expenditure on vitamin D retesting, and examined what proportion of patients are retested, if this was appropriate, and if vitamin D levels improved after retesting.
It found that those who are deficient or most at risk of deficiency, namely young adults aged 18 to 39, are the least likely to have their vitamin D levels monitored or rechecked by general practitioners.
The researchers said their findings show the need for a better understanding of the role of vitamin D testing in the population and for greater focus to be placed on monitoring vitamin D status in particular groups.
Young adults and males were most likely to have low vitamin D but were retested the least
Helena Scully, lead author of the report from Trinity’s School of Medicine and a Mercers Glanbia Bone Research Fellow, said clear guidelines on who should have their vitamin D retested are needed to identify deficiency.
“We have found that one in four patients have their vitamin D frequently checked by their GP, and yet some (23 per cent) remain deficient after several tests,” she said.
“Young adults and males were most likely to have low vitamin D but were retested the least. This shows those who are at most risk of vitamin D deficiency are not being assessed, leading to misdirection of resources from those who need it most.”
Surge in testing
The researchers said greater public awareness of vitamin D’s importance in bone health, along with its potential aid in supporting immunity against Covid-19 and other medical conditions, has led to a surge in the number of vitamin D tests in Ireland.
Ms Scully said the public should instead focus on getting enough vitamin D through their diet, with foods such as oily fish, egg yolk and fortified dairy products, and by taking a vitamin D supplement.
The researchers found that a third of vitamin D tests were done too frequently and more than half were in patients with adequate vitamin D levels.
A large proportion of tests are not being done on the right people or at the right time
Women were also more likely to have repeat tests, however they were less likely to be deficient.
The study suggests that a general practitioner ordering system for vitamin D requests be considered, that restricts it to pre-defined criteria, such as limiting retests within three months or to no more than two per year.
Dr Kevin McCarroll, study co-author and a consultant physician at James's Hospital, said: “The study shows that vitamin D retesting is prevalent yet a large proportion of tests are not being done on the right people or at the right time.
“It highlights the needs for a better understanding of the role of vitamin D retesting in the population and of the importance of getting enough vitamin D in the diet and/or via supplements, rather than having to check levels frequently.”