Serum bicarbonate and long-term outcomes in CKD.
BACKGROUND
A low serum bicarbonate level is prevalent in chronic kidney disease (CKD); however, its relationship to long-term outcomes is unclear.


METHODS
Cohort study.


METHODS
The Modification of Diet in Renal Disease (MDRD) Study examined the effects of dietary protein restriction and blood pressure control on progression of kidney disease. This analysis includes 942 screened but non-randomized individuals and 839 randomized participants with baseline serum bicarbonate measurements with stage 2-4 CKD.


METHODS
Serum bicarbonate level categorized into quartiles.


RESULTS
Kidney failure, all-cause mortality, and a composite outcome of mortality and kidney failure.


METHODS
Local laboratories at each participating site measured bicarbonate in fasting serum samples. Kidney failure outcomes were obtained from the US Renal Data System, and mortality data, from the National Death Index.


RESULTS
Mean glomerular filtration rate (GFR) was 39 ± 21 (SD) mL/min/1.73 m(2) and serum bicarbonate level was 23.3 ± 3.8 mEq/L. Kidney failure rates were 72%, 64%, 50%, and 41%; mortality rates were 31%, 25%, 21%, and 25%, and rates of the composite outcome were 78%, 71%, 58%, and 54% in bicarbonate quartiles 1, 2, 3, and 4, respectively. In analyses adjusted for demographic and cardiovascular disease factors, serum albumin level, proteinuria, and cause of kidney disease, compared with quartile 4, quartile 1 was associated with a 2.22 HR (95% CI, 1.83-2.68) of kidney failure; 1.39 HR (95% CI, 1.07-1.18) of all-cause mortality; and 1.36 HR (95% CI, 1.15-1.62) of the composite outcome. These associations were rendered nonsignificant with adjustment for GFR (kidney failure HR, 1.05 [95% CI, 0.87-1.28]; all-cause mortality HR, 0.99 [95% CI, 0.75-1.13]; composite HR, 1.04 [95% CI, 0.87-1.24]).


CONCLUSIONS
Single baseline measurement of serum bicarbonate.


CONCLUSIONS
Low serum bicarbonate level was associated with increased risk of long-term outcomes in nondiabetic patients with CKD. However, this risk is not independent of baseline GFR. Clinical trials are necessary to evaluate whether bicarbonate supplementation slows the progression of CKD.
Menon
Vandana
V
Division of Nephrology, Tufts Medical Center, Boston, MA 02111, USA. vandana.menon@gmail.com
Tighiouart
Hocine
H
Vaughn
Nubia Smith
NS
Beck
Gerald J
GJ
Kusek
John W
JW
Collins
Allan J
AJ
Greene
Tom
T
Sarnak
Mark J
MJ
D001639:Bicarbonates / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D002423:Cause of Death / Q000639:trends; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000401:mortality / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends; D013997:Time Factors; D014481:United States / Q000453:epidemiology
D001639:Bicarbonates; D015415:Biomarkers