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. 2014 May;55(5):271-80.
doi: 10.11622/smedj.2014071.

Vitamin D deficiency remains prevalent despite increased laboratory testing in New South Wales, Australia

Paul Quaggiotto  1 , Huy Tran, Marie Bhanugopan
Affiliations

Vitamin D deficiency remains prevalent despite increased laboratory testing in New South Wales, Australia

Paul Quaggiotto et al. Singapore Med J. 2014 May.

Abstract

Introduction: The aim of the present study was to assess the prevalence of vitamin D deficiency and toxicity, the frequency of 25-hydroxyvitamin D (25[OH]D) testing, and 25(OH)D variations with respect to patient gender, patient age and season in New South Wales, Australia.

Methods: A retrospective analysis of pathology records was performed to ascertain patient age, patient gender, sample collection date, plasma or serum 25(OH)D levels, calcium and parathyroid hormone (PTH) levels, and test numbers between 2001 and 2010. Linear regression with Bonferroni correction was used to calculate and compare age-adjusted mean 25(OH)D levels. Relationships of 25(OH)D with PTH and calcium were tested using Spearman's rank correlation.

Results: 25(OH)D testing increased by 730% over the ten-year study period. In 2010, many men (33%) and women (40%) were, to some degree, vitamin D deficient (≤ 50 nmol/L). Vitamin D toxicity was rare, with only one instance noted. 25(OH)D levels correlated positively with calcium and negatively with PTH levels. 25(OH)D levels decreased with age. In 2010, 25(OH)D levels were highest in February and lowest in September/October. Cyclical variation was observed for 25(OH)D levels between 2006 and 2010.

Conclusion: We found that vitamin D deficiency was prevalent in both men and women, with a higher prevalence in the latter, despite the substantial increased demand for 25(OH)D testing in our population over the decade. Vitamin D deficiency was associated with elevated PTH levels. Vitamin D toxicity was rare and only observed once during our study period. 25(OH)D levels decreased with age and varied with season, with the highest levels observed in late summer and the lowest in early spring.

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Figures

Fig. 1
Fig. 1
Gender-wise breakdown of 25-hydroxyvitamin D testing over the 2001–2010 period.
Fig. 2
Fig. 2
Gender-wise frequency distribution of serum or plasma 25-hydroxyvitamin D levels in 2010.
Fig. 3
Fig. 3
Gender-wise age-adjusted mean serum or plasma 25-hydroxyvitamin D levels over the 2001–2010 period. Note: Values are expressed as age-adjusted mean ± standard error of the mean. *Significantly highest means during the 2006–2010 period. †Significantly lowest means during the 2006–2010 period (p < 0.001).
Fig. 4
Fig. 4
Serum or plasma parathyroid hormone (PTH) levels versus 25-hydroxyvitamin D (25[OH]D) levels in 2010. Note: To aid the visual presentation of data, one outlying point (PTH 0.4 pmol/L; 25(OH)D 840 nmol/L) was omitted from the figure but not from the data analysis.
Fig. 5
Fig. 5
Serum or plasma calcium levels versus 25-hydroxyvitamin D (25[OH]D) levels over the 2001–2010 period. Note: To aid the visual presentation of data, one outlying point (calcium 2.81 mmol/L; 25(OH)D = 840 nmol/L) was omitted from the figure but not from the data analysis.
Fig. 6
Fig. 6
Gender-wise frequency distribution of serum or plasma 25-hydroxyvitamin D testing in 2010, according to age group.
Fig. 7
Fig. 7
Gender-wise unadjusted mean serum or plasma 25-hydroxyvitamin D levels in 2010, according to age group. *Significantly highest means (p < 0.05). †Significantly lowest means.
Fig. 8
Fig. 8
Gender-wise monthly age-adjusted mean serum or plasma 25-hydroxyvitamin D levels in 2010. *Significantly highest means (p < 0.05). †Significantly lowest means.
Fig. 9
Fig. 9
Gender-wise monthly age-adjusted mean serum or plasma 25-hydroxyvitamin D levels over the 2006–2010 five-year period.
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