Serum 25-hydroxyvitamin D deficiency; a risk factor for chronic kidney disease in ambulatory indigent patients

To assess whether 25-hydroxyvitamin D (25[OH]D) deficiency is a risk factor for chronic kidney disease (CKD) in ambulatory indigent patients.

Data for all serum 25(OH)D concentrations measured during 2010 in our ambulatory nondialysis-dependent patients were analyzed along with CKD-related parameters. Patients were stratified into groups based on 25(OH)D levels of <10, 10 to 19, 20 to 29, and ≥30 ng/mL. CKD was defined by estimated glomerular filtration rate (eGFR; Chronic Kidney Disease-Epidemiology Collaboration [CKD-EPI] equation) and abnormal urine protein to creatinine ratios. CKD-associated parameters included serum parathyroid hormone (PTH), 1,25-dihydroxyvitamin D (1,25[OH]2D), alkaline phosphatase, albumin, corrected calcium, and total CO2 levels.

A total of 2,811 patients had 25(OH)D levels measured. Patients with 25(OH)D levels <10 ng/mL had significantly increased relative risk (RR) of an eGFR <15 mL/min/1.73 m2 (RR, 4.0), an eGFR of 15 to 29 mL/min/1.73 m2 (RR, 2.6), urine protein to creatinine ratio >3.5 g/g (RR, 5.6), and serum PTH >100 pg/mL (RR, 2.8) compared to patients with a 25(OH)D level ≥30 ng/mL. Patients with 25(OH)D levels of 10 to19 ng/mL had significantly increased RR of a urine protein to creatinine ratio >3.5 g/g (RR, 4.8) and serum PTH >100 pg/mL (RR, 1.5) compared to patients with 25(OH)D levels ≥30 ng/mL.

25(OH)D deficiency (<10 ng/mL) was associated with reduced eGFR, nephrotic-range proteinuria, and increased PTH levels in our population of ambulatory urban indigent patients.