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      A Critical Evaluation of Glycated Protein Parameters in Advanced Nephropathy: A Matter of Life or Death : A1C remains the gold standard outcome predictor in diabetic dialysis patients

      , MD, MPH, PHD

      Diabetes Care

      American Diabetes Association

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          Abstract

          Chronic kidney disease remains as one of the major complications for individuals with diabetes and contributes to considerable morbidity. Individuals subjected to dialysis therapy, half of whom are diabetic, experience a mortality of ∼20% per year. Understanding factors related to mortality remains a priority. Outside of dialysis units, A1C is unquestioned as the “gold standard” for glycemic control. In the recent past, however, there is evidence in large cohorts of diabetic dialysis patients that A1C at both the higher and lower levels was associated with mortality. Given the unique conditions associated with the metabolic dysregulation in dialysis patients, there is a critical need to identify accurate assays to monitor glycemic control to relate to cardiovascular endpoints. In this two-part point-counterpoint narrative, Drs. Freedman and Kalantar-Zadeh take opposing views on the utility of A1C in relation to cardiovascular disease and survival and as to consideration of use of other short-term markers in glycemia. In the narrative preceeding this counterpoint, Dr. Freedman suggests that glycated albumin may be the preferred glycemic marker in dialysis subjects. In the counterpoint narrative below, Dr. Kalantar-Zadeh defends the use of A1C as the unquestioned gold standard for glycemic management in dialysis subjects.

          —William T. Cefalu, MD Editor in Chief, Diabetes Care

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          Most cited references 29

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          Association between glycemic control and adverse outcomes in people with diabetes mellitus and chronic kidney disease: a population-based cohort study.

          Better glycemic control as reflected by lower hemoglobin A(1c) (HbA(1c)) level may prevent or slow progression of nephropathy in people with diabetes mellitus (DM). Whether a lower HbA(1c) level improves outcomes in people with DM and chronic kidney disease (CKD) is unknown. From all people with serum creatinine measured as part of routine care in a single Canadian province from 2005 through 2006, we identified those with CKD based on laboratory data (estimated glomerular filtration rate [eGFR], <60.0 mL/min/1.73 m(2)]) and DM using a validated algorithm applied to hospitalization and claims data. Patients were classified based on their first HbA(1c) measurement; Cox regression models were used to assess independent associations between HbA(1c) level and 5 study outcomes (death, progression of kidney disease based on a doubling of serum creatinine level, or new end-stage renal disease [ESRD], cardiovascular events, all-cause hospitalization). We identified 23,296 people with DM and an eGFR lower than 60.0 mL/min/1.73 m(2). The median HbA(1c) level was 6.9% (range, 2.8%-20.0%), and 11% had an HbA(1c) value higher than 9%. Over the median follow-up period of 46 months, 3665 people died, and 401 developed ESRD. Regardless of baseline eGFR, a higher HbA(1c) level was strongly and independently associated with excess risk of all 5 outcomes studied (P < .001 for all comparisons). However, the association with mortality was U-shaped, with increases in the risk of mortality apparent at HbA(1c) levels lower than 6.5% and higher than 8.0%. The increased risk of ESRD associated with a higher HbA(1c) level was attenuated at a lower baseline eGFR (P value for interaction, <.001). Specifically, among those with an eGFR of 30.0 to 59.9 mL/min/1.73 m(2), the risk of ESRD was increased by 22% and 152% in patients with HbA(1c) levels of 7% to 9% and higher than 9%, respectively, compared with patients with an HbA(1c) level lower than 7% (P < .001), whereas corresponding increases were 3% and 13%, respectively, in those with an eGFR of 15.0 to 29.9 mL/min/1.73 m(2). A hemoglobin A(1c) level higher than 9% is common in people with non-hemodialysis-dependent CKD and is associated with markedly worse clinical outcomes; lower levels of HbA(1c) (<6.5%) also seemed to be associated with excess mortality. The excess risk of kidney failure associated with a higher HbA(1c) level was most pronounced among people with better kidney function. These findings suggest that appropriate and timely control of HbA(1c) level in people with DM and CKD may be more important than previously realized, but suggest also that intensive glycemic control (HbA(1c) level <6.5%) may be associated with increased mortality.
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            Comparison of glycated albumin and hemoglobin A(1c) levels in diabetic subjects on hemodialysis.

            Glycated albumin is thought to more accurately reflect glycemic control in diabetic hemodialysis patients than hemoglobin A(1c) because of shortened red cell survival. To test this, glycated hemoglobin and albumin levels were measured in blood samples collected from 307 diabetic subjects of whom 258 were on hemodialysis and 49 were without overt renal disease. In diabetic subjects with renal disease, relative to those without, the mean serum glucose and glycated albumin concentrations were significantly higher while hemoglobin A(1c) tended to be lower. The glycated albumin to hemoglobin A(1c) ratio was significantly increased in dialysis patients compared with the controls. Hemoglobin A(1c) was positively associated with hemoglobin and negatively associated with the erythropoietin dose in hemodialysis patients, whereas these factors and serum albumin did not significantly impact glycated albumin levels. Using best-fit multivariate models, dialysis status significantly impacted hemoglobin A(1c) levels without a significant effect on glycated albumin. Our results show that in diabetic hemodialysis patients, hemoglobin A(1c) levels significantly underestimate glycemic control while those of glycated albumin more accurately reflect this control.
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              Serum albumin as a predictor of mortality in peritoneal dialysis: comparisons with hemodialysis.

              Serum albumin level predicts mortality in dialysis patients and is used to assess their health status and the quality of delivered care. Whether the threshold level of serum albumin at which mortality risk increases in peritoneal dialysis (PD) patients is the same as for hemodialysis (HD) patients has not been studied. Observational cohort study of dialysis patients undertaken to determine the survival-predictability of serum albumin level in PD patients and compare it with that in HD patients. 130,052 dialysis patients (PD, 12,171; HD, 117,851) who received treatment in any of the 580 dialysis units owned by DaVita Inc between July 1, 2001, through June 30, 2006, followed up through June 30, 2007. Baseline and time-averaged serum albumin level (assayed using bromcresol green) and change in serum albumin level over 6 months. All-cause, cardiovascular, and infection-related mortality. PD patients with baseline serum albumin level <3.0 g/dL had a more than 3-fold higher adjusted risk of all-cause and cardiovascular mortality and 3.4-fold higher risk of infection-related mortality (reference group: serum albumin, 4.00-4.19 g/dL). Adjusted all-cause mortality was significantly lower in PD patients with a ≥0.3-g/dL increase in serum albumin level over 6 months and significantly higher in those for whom it decreased by ≥0.2 g/dL (reference group: serum albumin change, +0.1 to -0.1 g/dL). A significant increase in death risk was evident for HD patients with serum albumin level <4.0 g/dL, but at <3.8 g/dL for PD patients. For each albumin category, overall death risk for PD patients was lower than for HD patients (reference group: HD patients with serum albumin of 4.00-4.19 g/dL). Study can identify associations only without attribution of causality and residual confounding cannot be excluded. Serum albumin predicts all-cause, cardiovascular, and infection-related mortality in both PD and HD patients. However, the threshold at which risk of death increases varies by dialysis modality, and this difference should be considered by agencies or organizations that set quality standards. Copyright © 2011 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.
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                Author and article information

                Journal
                Diabetes Care
                Diabetes Care
                diacare
                dcare
                Diabetes Care
                Diabetes Care
                American Diabetes Association
                0149-5992
                1935-5548
                July 2012
                12 June 2012
                : 35
                : 7
                : 1625-1628
                Affiliations
                From the Harold Simmons Center for Kidney Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California; the David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, California; and the Fielding School of Public Health at the University of California, Los Angeles, Los Angeles, California
                Author notes
                Corresponding author: Kamyar Kalantar-Zadeh, kamkal@ 123456ucla.edu .
                Article
                0483
                10.2337/dc12-0483
                3379587
                22723587
                © 2012 by the American Diabetes Association.

                Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.

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                Point-Counterpoint

                Endocrinology & Diabetes

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