Journal Article

A threshold value of estimated glomerular filtration rate that predicts changes in serum 25-hydroxyvitamin D levels: 4th Korean National Health and Nutritional Examination Survey 2008

Yun Jung Oh, Myounghee Kim, Hajeong Lee, Jung Pyo Lee, Ho Kim, Sejoong Kim, Kook-Hwan Oh, Kwon Wook Joo, Chun Soo Lim, Suhnggwon Kim, Yon Su Kim and Dong Ki Kim

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 27, issue 6, pages 2396-2403
Published in print June 2012 | ISSN: 0931-0509
Published online January 2012 | e-ISSN: 1460-2385 | DOI: http://dx.doi.org/10.1093/ndt/gfr763
A threshold value of estimated glomerular filtration rate that predicts changes in serum 25-hydroxyvitamin D levels: 4th Korean National Health and Nutritional Examination Survey 2008

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Background.

Vitamin D deficiency is known as an important risk factor for mortality in patients with chronic kidney disease (CKD). Nevertheless, the association of renal function itself with vitamin D status or serum 25-hydroxyvitamin D (25OHD) level has not been investigated thoroughly.

Methods.

We examined the association between the estimated glomerular filtration rate (eGFR) and serum 25OHD levels using data from the 4th Korean National Health and Nutritional Examination Survey 2008. Generalized additive models (GAMs) were used to examine the relationship between eGFR and serum 25OHD levels and to estimate a threshold value of eGFR that predicts changes in serum 25OHD levels.

Results.

The mean serum 25OHD level was 20.4 ± 9.1 ng/mL, and the overall prevalence of vitamin D deficiency was 29.9% in this population. The prevalence of vitamin D deficiency began to increase at eGFR levels <45 mL/min/1.73m2. After adjustment, the logistic regression of dichotomized eGFR levels with a cut-point of 45 mL/min/1.73m2 yielded an increased odds ratio for vitamin D deficiency. Additionally, the continuous relationship between eGFR and 25OHD levels was explored using GAMs adjusted for various confounding factors. In this analysis, the difference from the mean serum 25OHD started to increase below an eGFR threshold of 55.4 mL/min/1.73m2, which suggests that renal function is directly related to the serum 25OHD levels in patients with CKD Stages 3–5.

Conclusion.

Although moderate renal dysfunction (eGFR < 45 mL/min/1.73m2) is an important predictor of vitamin D deficiency, serum 25OHD levels start to decrease below an eGFR level of ∼60 mL/min/1.73m2 independent of other risk factors. These results suggest that more careful attention to 25OHD levels may be needed when patients reach Stage 3 CKD.

Keywords: epidemiology; proteinuria; renal function; threshold; vitamin D deficiency

Journal Article.  5009 words.  Illustrated.

Subjects: Nephrology

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