Replacement therapy may reverse low hemoglobin levels in CKD patients.
GRAPEVINE, Tex.—Higher levels of 25-hydroxyvitamin D (25 (OH) D) may lower the risk of anemia and elevated C-reactive protein levels may raise the risk, according to new study findings that may explain much of the high prevalence of anemia among individuals with kidney disease, researchers conclude.
Jessica Kendrick, MD, and her colleagues at the University of Colorado Health Sciences Center in Denver examined data from a population-based sample of 16,301 subjects aged 18 years and older who participated in the Third National Health and Nutrition Examination Survey (NHANES III) conducted from 1988 to 1994.
The researchers categorized subjects according to estimated glomerular filtration rate (GFR): less than 30, 30-59, 60-89, and 90 mL/min per 1.73 m2 or higher. Individuals with with an eGFR of 30-59 and less than 30 mL/min per 1.73 m2 were at two times and 28 times higher risk of anemia (hemoglobin level below 12 g/dL) compared with those with an eGFR of 90 mL/min per 1.73 m2 and higher.
Additionally, as eGFR declined, 25 (OH) D levels decreased and CRP levels increased. Further analysis showed that 25 (OH) D and CRP levels independently predicted hemoglobin levels. Each 10 ng/mL increment in 25 (OH) D was associated with a 29% reduced risk of anemia, after adjusting for age, gender, race, weight, and other potential confounders, Dr. Kendrick reported here at the 2008 Spring Clinical Meetings sponsored by the National Kidney Foundation (NKF).
Additionally, each 10 mg/dL increment in CRP level was associated with a 68% increased risk of anemia. Study findings suggest that replacing vitamin D in patients with low levels of this vitamin may boost hemoglobin levels, Dr. Kendrick said. CKD patients have a high prevalence of 25 (OH) D deficiency.
Vitamin D may influence hemoglobin through its effect on inflammation, she explained. Data show that supplementation with 25 (OH) D is associated with reductions in pro-inflammatory cytokines, she noted.
In a separate study presented at the conference, the same investigators reported on an analysis of 16,864 NHANES III participants showing that decreasing 25 (OH) D levels were significantly associated with increasing prevalence of CVD in the entire study population. The team observed no significant association between 25 (OH) D levels and CVD among subjects with CKD.
Also at the conference, a research team from the University of Texas Health Science Center in San Antonio reported on a study suggesting that current guidelines developed as part of the NKF’s Kidney Disease Outcomes Quality Initiative (K/DOQI) are inadequate for correcting vitamin D deficiency/insufficiency (VDDI) in non-dialyzing CKD patients.
Of 225 patients with VDDI, 70 were treated with ergocalciferol according to K/DOQI treatment guidelines. The percentage of patients who achieved K/DOQI target vitamin D levels was 20% for CKD stages 1 and 2, and 16%, 10%, and 30% for CKD stages 3, 4, and 5, respectively. “Alternative treatment regimens of vitamin D supplementation in these patients are required,” the authors concluded.