Vitamin D tests for children increased 30-fold over 15 years: Study

A recent study has suggested the odds of a vitamin D test being ordered among children rose 30-fold within 15 years, with researchers saying there was little difference in the rate of low diagnoses.
 
The findings, which have been published in the BMJ paediatric journal Archives of Disease in Childhood, were based on analysis of a dataset from three Primary Health Networks in Victoria for 25OHD tests ordered by GPs from 2003–18.
 
Authors from the University of Queensland and Macquarie University found the odds of a test being ordered for children was 30 times the rate in 2018 compared to 15 years previously, but the rate of detecting a low 25OHD level remained stable.
 
They also noted a higher rate of testing in winter, as well as among adolescents aged 14–18 years compared to infants up to the age of one.
 
Of the 61,809 tests – which were conducted among 46,960 children aged 0–18 – 22,391 (or 36.2%) were marked as low in vitamin D, while 24,467 (39.6%) were normal and 63 (0.1%) as high. Almost a quarter of the tests were unmarked.
 
The authors also note that children and adolescents whose tests indicated vitamin D deficiency had a repeat test within three months in only 3.9% of cases compared to 19.2% when the initial tests showed normal vitamin D levels.
 
‘The reasons for these seemingly counterintuitive follow-up practices are unclear and do not align with current recommendations,’ the authors wrote.
 
‘Low rates of retesting, after detection of deficiency, may be related to onward referral for specialist care; however, the dataset contained no information about referrals.’
 
Co-author Professor Yvonne Zurynski, from Macquarie University’s Australian Institute of Health Innovation, called the results ‘symptomatic of low-value care’.
 
‘These findings add to previous research by international experts who recommend that testing for vitamin D deficiency without symptoms is unnecessary,’ she said.
 
‘However, this advice doesn’t appear to have taken root in general practice in Australia.’
 
The authors note that the study ‘may not be generalisable’ across Australia, although they state that the patterns uncovered align with national MBS data.
 
Since the timeframe covered by the study, there has been a further rise in the use of MBS item number 66833, the patient rebate for the blood test.
 
In the 2018–2019 financial year it was recorded 3,719,571 times, while in the most recent financial year Services Australia reports its use on 5,363,731 occasions – a 44% increase.
 
The issue of over-testing for low vitamin D levels has previously been covered by newsGP.
 
The RACGP’s First do no harm: A guide to choosing wisely recommends that GPs should not routinely measure vitamin D in the general population, and includes guidance for dealing with requests for testing when not clinically indicated.
 
In 2014, changes to restrict the use of vitamin D testing were introduced, which authors of the BMJ article found caused an initial decrease in testing rates, before a return to previous growth.
 
The authors of the BMJ article acknowledged the dataset they used did not include details about children’s symptoms, or their risk factors for vitamin D deficiency or nutritional rickets such as existing medical conditions, skin colour and ethnicity.
 
They also called for a ‘national unified, pathology data resource’ to support future research on a larger scale, and said more work is needed to identify what drives decision-making for ordering 25OHD tests.
 
The college’s ‘First do no harm’ resources are available on the RACGP website. GPs can create a quick log to self-record CPD points.
 
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paediatrics pathology vitamin D