Session: OR45-What Is New in Vitamin D?
Room 29 (San Diego Convention Center)
Method. Total 25(OH)D was determined using liquid chromatography—tandem mass spectrometry. We evaluated all 25(OH)D tests performed for adults (≥18 years old) for a 12-month period starting in November 2009 (1.6 million tests) and August 2013 (1.2 million tests). Intact PTH was measured by a chemiluminescence-based assay. The results were compared using Z-test after Box-Cox transformation to satisfy the Gaussian distribution assumption.
Results. The mean 25(OH)D value increased from 27.2±0.02 ng/mL pre-guidelines to 32.5±0.03 ng/mL post-guidelines (P <0.0001). The proportion of patients with deficient vitamin D levels decreased significantly from the pre-guideline period to the post-guideline period (22.1% vs 14.5%), as did the proportion with insufficient levels (33.7% pre-guidelines vs 28.1% post-guidelines) (both P <0.0001). No clinically significant changes in vitamin D2 levels were noted between pre- and post-guideline groups. The percentage of iPTH results above the upper limit of the reference range decreased from 50% in 2009 to 39% in 2014 (P <0.0001).
Conclusion. We observed an increase in the mean value of 25(OH)D in the adult population, with concomitant decreases in the percentage of patient specimens classified as deficient or insufficient 25(OH)D post-guidelines. Possible explanations for these results include 1) a positive impact on patient 25(OH)D concentrations after introduction of the new guidelines; or 2) testing may have shifted to people who were more likely to have optimal levels of 25(OH)D in the post-guideline period. The fall in the percent of elevated iPTH results corresponds, as expected, to the rise in the 25(OH)D levels.
Nothing to Disclose: PW, JEW, WW, PWM
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