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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Medicine, University of Southern California.
Elaine M
EM
Kaptein
Department of Medicine, University of Southern California.
San San
SS
Yi
Department of Pathology, University of Southern California.
David B
DB
Endres
Regional Research Laboratory, Kaiser Permanente, Los Angeles, California.
John S
JS
Kaptein
Department of Pediatrics, University of Southern California.
Linda S
LS
Chan
D000328:Adult; D000368:Aged; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D051436:Renal Insufficiency, Chronic / Q000209:etiology*; D012189:Retrospective Studies; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications*
D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D