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Percent who are Vitamin D Deficient: 6, 9, or 22 – depends on testing system – Oct 2014

Assessment of low vitamin D among Saudi Arabians. Did we overshoot the runway?

Saudi Med J. 2014 Oct;35(10):1243-9.
Sadat-Ali M1, Al-Elq AH, Al-Shaikh IH, Al-Turki HA, Al-Ali AK, Al-Othman AA.
1Department of Orthopedic Surgery, College of Medicine, King Fahd Hospital of the University, University of Dammam, Dammam, Kingdom of Saudi Arabia. E-mail. drsadat at hotmail.com.

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OBJECTIVES:
To compare the performance of 3 commonly used 25-hydroxyvitamin D (25-OHD) assays among a sample of the Saudi population.
METHODS:
This cross-sectional study was carried out between January 2011 and December 2012 at King Fahd Hospital of the University, Al-Khobar, Saudi Arabia. After informed consent, blood samples for measurement of 25-OHD level was extracted from 200 adults. The vitamin D level of each individual were determined using chemiluminescence immunoassay (CLIA), radio-immuno assay (RIA), and liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay. Assays were also compared through commonly used cut-points for classification of vitamin D deficiency. Bias between assays was evaluated using Bland-Altman plots.
RESULTS:
The average age of patients was 45.7+/-16.1 years. A significant difference between the assays was found. The mean 25-OHD levels were highest for the LC-MS/MS (21.65 ng/mL, 95% CI 19.74-23.56), intermediate for RIA (16.607 ng/mL, 95% CI 14.87-18.32), and lowest for CLIA method (13.864 ng/mL, 95% CI 12.109-15.618). Using 30 ng/mL as a cutoff value, only 6% was found to have normal levels of 25-OHD using CLIA, 9% using RIA, and 22% using LC-MS/MS.
CONCLUSION:
Levels of 25-OHD and the prevalence of vitamin D deficiency are dependent on the assay used. The reported high prevalence of hypovitaminosis D among the Saudi population can be partially explained by the use of assays that underestimate vitamin D levels.
PMID: 25316470

Attached files

ID Name Comment Uploaded Size Downloads
6023 Test results F1.jpg admin 07 Oct, 2015 11.08 Kb 861
6022 Differences between testers.pdf admin 07 Oct, 2015 1.00 Mb 944