Prevalence and influencing factors of vitamin D deficiency in chronic kidney disease: A cross-sectional study.

BACKGROUND AND OBJECTIVES

Very few studies have investigated vitamin D deficiency of Chinese chronic kidney disease (CKD) patients. Our main aims were to measure 25(OH)D levels and to explore the possible correlated factors contributing to vitamin D deficiency.

MATERIALS AND METHODS

207 patients who came from north China and were not receiving vitamin D supplementation were included in this study from February 2013 to April 2015. We collected blood samples to determine levels of serum creatinine (Scr), blood urea nitrogen (BUN), uric acid (UA), serum phosphate (P) and calcium (Ca), intact parathyroid hormone (iPTH), albumin (ALB), as well as urinary protein within 24 hours (24hUPr). Total 25(OH)D was measured via electrochemiluminescence immunoassay. Vitamin D deficiency should be defined as a 25(OH)D < 15 ng/mL.

RESULTS

Of the 207 patients, only 20.3% had a circulating 25(OH)D level > 15 ng/mL. The concentrations of 25(OH)D were 11.73 ± 6.75 ng/mL, 10.44 ± 6.03 ng/mL, 10.05 ± 5.57 ng/mL, 9.10 ± 5.00 ng/mL, 7.13 ± 3.99 ng/mL (p < 0.001) according to estimated glomerular filtration rate (eGFR) (89 - 60, 59 - 45, 44 - 30, 29 - 15, < 15 mL/min/1.73m). The prevalence of 25(OH)D deficiency was significantly high in each group (70.1%, 70.8%, 76.5%, 81.6%, 91.4%, p < 0.001). 25(OH)D concentration decreased with the decline of renal function. The difference of 25(OH)D levels between the 24hUPr ≥ 3.5 g group and the 24hUPr < 3.5 g group was statistically significant. Multivariate linear regression analysis showed that 25(OH)D concentration was associated with 24hUPr and serum Ca. The 25(OH)D concentration was lower, and the prevalence of 25(OH)D deficiency was higher in diabetes mellitus (DM) patients compared with patients without DM.

CONCLUSION

This study shows a high prevalence of 25(OH)D deficiency in CKD patients from north China, and the deficiency is dependent on eGFR. Urinary protein and serum Ca might be associated with 25(OH)D concentration. DM patients have lower 25(OH)D concentrations than non-DM patients.