ORIGINAL PAPER
Measuring vitamin D levels: surrogates are insufficient A. H. Heald,1,2 S. G. Anderson,3 J. J. Scargill,4 A. D. Short,5 D. Holland,6 M. Livingston,7 A. A. Fryer,6 R. P. Donn1
1
SUMMARY
What’s known
Aims: With the increasing evidence of adverse consequences because of low vitamin D levels on health demand for vitamin D, screening is increasing.The objective of the study was to assess whether parathyroid hormone (PTH) levels/bone profile is sufficient to identify patients with vitamin D insufficiency or deficiency, or whether vitamin D should be measured directly. Methodology: A total of 1560 serum specimens, with requests for 25-hydroxyvitamin D (25-OH vitamin D), calcium, phosphate, alkaline phosphatase (ALP), creatinine and PTH on the same sample were analysed at Salford Royal Hospital from November 2010 to November 2012. Results: The prevalence of total vitamin D insufficiency or deficiency (defined as total 25-OH vitamin D < 50 nmol/l) was 62.9% (981/1560) overall, with males having higher proportions (67.2 vs. 59.3 per cent; v2 = 8.78, p = 0.003). There was no overall trend in mean serum adjusted calcium across categories of 25-OH vitamin D status but mean serum phosphate was significantly lower (F = 6.53, p < 0.0001) in patients with a 25-OH vitamin D level < 50 nmol/l. However in patients with vitamin D deficiency, a significant proportion had PTH, calcium, phosphate and alkaline phosphatase levels within the laboratory normal range. Even at a 25-OH vitamin D < 10 nmol/l, 71.6% had a normal PTH, 89.8% had normal serum calcium levels, 84.9% had normal phosphate levels and 81.6% had normal serum ALP. Conclusions: Therefore, despite the costs associated with the measurement of vitamin D, our findings show that no surrogate is adequate for screening for vitamin D deficiency.
Introduction Vitamin D insufficiency and deficiency are related to a range of adverse health outcomes (1). In the UK, vitamin D deficiency has been generally defined as 25-hydroxyvitamin D (25-OH vitamin D) < 25 nmol/l (2), or < 50 nmol/l (3), and insufficiency in vitamin D has been defined as < 50 nmol/l (2) or
Measuring vitamin D levels: surrogates are insufficient A. H. Heald,1,2 S. G. Anderson,3 J. J. Scargill,4 A. D. Short,5 D. Holland,6 M. Livingston,7 A. A. Fryer,6 R. P. Donn1
1
SUMMARY
What’s known
Aims: With the increasing evidence of adverse consequences because of low vitamin D levels on health demand for vitamin D, screening is increasing.The objective of the study was to assess whether parathyroid hormone (PTH) levels/bone profile is sufficient to identify patients with vitamin D insufficiency or deficiency, or whether vitamin D should be measured directly. Methodology: A total of 1560 serum specimens, with requests for 25-hydroxyvitamin D (25-OH vitamin D), calcium, phosphate, alkaline phosphatase (ALP), creatinine and PTH on the same sample were analysed at Salford Royal Hospital from November 2010 to November 2012. Results: The prevalence of total vitamin D insufficiency or deficiency (defined as total 25-OH vitamin D < 50 nmol/l) was 62.9% (981/1560) overall, with males having higher proportions (67.2 vs. 59.3 per cent; v2 = 8.78, p = 0.003). There was no overall trend in mean serum adjusted calcium across categories of 25-OH vitamin D status but mean serum phosphate was significantly lower (F = 6.53, p < 0.0001) in patients with a 25-OH vitamin D level < 50 nmol/l. However in patients with vitamin D deficiency, a significant proportion had PTH, calcium, phosphate and alkaline phosphatase levels within the laboratory normal range. Even at a 25-OH vitamin D < 10 nmol/l, 71.6% had a normal PTH, 89.8% had normal serum calcium levels, 84.9% had normal phosphate levels and 81.6% had normal serum ALP. Conclusions: Therefore, despite the costs associated with the measurement of vitamin D, our findings show that no surrogate is adequate for screening for vitamin D deficiency.
Introduction Vitamin D insufficiency and deficiency are related to a range of adverse health outcomes (1). In the UK, vitamin D deficiency has been generally defined as 25-hydroxyvitamin D (25-OH vitamin D) < 25 nmol/l (2), or < 50 nmol/l (3), and insufficiency in vitamin D has been defined as < 50 nmol/l (2) or
