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      Tubular secretion of creatinine and kidney function: an observational study

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          Abstract

          Background

          Prior papers have been inconsistent regarding how much creatinine clearance (CrCl) overestimates glomerular filtration rate (GFR). A recent cross-sectional study suggested that measurement error alone could entirely account for the longstanding observation that CrCl/GFR ratio is larger when GFR is lower among patients with chronic kidney disease (CKD); but there have been no validation of this in other cohorts.

          Methods

          To fill these gaps in knowledge regarding the relation between CrCl and GFR, we conducted cross-sectional and longitudinal analysis of the Modification of Diet in Renal Disease study (MDRD) and African American Study of Kidney Disease and Hypertension (AASK); and cross-sectional analysis of a clinical dataset from the Mayo Clinic of four different patient populations (CKD patients, kidney transplant recipients, post kidney donation subgroup and potential kidney donors). In the cross-sectional analyses (MDRD, AASK and Mayo Clinic cohort), we examined the relation between the CrCl/iothalamate GFR (iGFR) ratio at different categories of iGFR or different levels of CrCl. In the MDRD and AASK longitudinal analyses, we studied how the CrCl/iGFR ratio changed with those who had improvement in iGFR (CrCl) over time versus those who had worsening of iGFR (CrCl) over time.

          Results

          Observed CrCl/iGFR ratios were generally on the lower end of the range reported in the literature for CKD (median 1.24 in MDRD, 1.13 in AASK and 1.25 in Mayo Clinic cohort). Among CKD patients in whom CrCl and iGFR were measured using different timed urine collections, CrCl/iGFR ratio were higher with lower iGFR categories but lower with lower CrCl categories. However, among CKD patients in whom CrCl and iGFR were measured using the same timed urine collections (which reduces dis-concordant measurement error), CrCl/iGFR ratio were higher with both lower iGFR categories and lower CrCl categories.

          Conclusions

          These data refute the recent suggestion that measurement error alone could entirely account for the longstanding observation that CrCl/GFR ratio increases as GFR decreases in CKD patients. They also highlight the lack of certainty in our knowledge with regard to how much CrCl actually overestimates GFR.

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          Most cited references33

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          Effect of blood pressure lowering and antihypertensive drug class on progression of hypertensive kidney disease: results from the AASK trial.

          Hypertension is a leading cause of end-stage renal disease (ESRD) in the United States, with no known treatment to prevent progressive declines leading to ESRD. To compare the effects of 2 levels of blood pressure (BP) control and 3 antihypertensive drug classes on glomerular filtration rate (GFR) decline in hypertension. Randomized 3 x 2 factorial trial with enrollment from February 1995 to September 1998. A total of 1094 African Americans aged 18 to 70 years with hypertensive renal disease (GFR, 20-65 mL/min per 1.73 m(2)) were recruited from 21 clinical centers throughout the United States and followed up for 3 to 6.4 years. Participants were randomly assigned to 1 of 2 mean arterial pressure goals, 102 to 107 mm Hg (usual; n = 554) or 92 mm Hg or less (lower; n = 540), and to initial treatment with either a beta-blocker (metoprolol 50-200 mg/d; n = 441), an angiotensin-converting enzyme inhibitor (ramipril 2.5-10 mg/d; n = 436) or a dihydropyridine calcium channel blocker, (amlodipine 5-10 mg/d; n = 217). Open-label agents were added to achieve the assigned BP goals. Rate of change in GFR (GFR slope); clinical composite outcome of reduction in GFR by 50% or more (or > or =25 mL/min per 1.73 m2) from baseline, ESRD, or death. Three primary treatment comparisons were specified: lower vs usual BP goal; ramipril vs metoprolol; and amlodipine vs metoprolol. Achieved BP averaged (SD) 128/78 (12/8) mm Hg in the lower BP group and 141/85 (12/7) mm Hg in the usual BP group. The mean (SE) GFR slope from baseline through 4 years did not differ significantly between the lower BP group (-2.21 [0.17] mL/min per 1.73 m2 per year) and the usual BP group (-1.95 [0.17] mL/min per 1.73 m2 per year; P =.24), and the lower BP goal did not significantly reduce the rate of the clinical composite outcome (risk reduction for lower BP group = 2%; 95% confidence interval [CI], -22% to 21%; P =.85). None of the drug group comparisons showed consistent significant differences in the GFR slope. However, compared with the metoprolol and amlodipine groups, the ramipril group manifested risk reductions in the clinical composite outcome of 22% (95% CI, 1%-38%; P =.04) and 38% (95% CI, 14%-56%; P =.004), respectively. There was no significant difference in the clinical composite outcome between the amlodipine and metoprolol groups. No additional benefit of slowing progression of hypertensive nephrosclerosis was observed with the lower BP goal. Angiotensin-converting enzyme inhibitors appear to be more effective than beta-blockers or dihydropyridine calcium channel blockers in slowing GFR decline.
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            Limitations of creatinine as a filtration marker in glomerulopathic patients.

            To determine the reliability of creatinine as a measure of the glomerular filtration rate (GFR), we compared the simultaneous clearance of creatinine to that of three true filtration markers of graded size in 171 patients with various glomerular diseases. Using inulin (radius [rs] = 15 A) as a reference marker, we found that the fractional clearance of 99mTc-DTPA (rs = 4 A) was 1.02 +/- 0.14, while that of a 19 A rs dextran was 0.98 +/- 0.13, with neither value differing from unity. In contrast, the fractional clearance (relative to inulin) of creatinine (rs = 3 A) exceeded unity, averaging 1.64 +/- 0.05 (P less than 0.001), but could be lowered towards unity by acute blockade of tubular creatinine secretion by IV cimetidine. Cross-sectional analysis of all 171 patients revealed fractional creatinine secretion to vary inversely with GFR. This inverse relationship was confirmed also among individual patients with either deteriorating (N = 28) or remitting (N = 26) glomerular disease, who were studied longitudinally. As a result, changes in creatinine relative to inulin clearance were blunted considerably or even imperceptible. We conclude that true filtration markers with rs less than 20 A, including inulin, are unrestricted in glomerular disease, and that creatinine is hypersecreted progressively by remnant renal tubules as the disease worsens. Accordingly, attempts to use creatinine as a marker with which to evaluate or monitor glomerulopathic patients will result in gross and unpredictable overestimates of the GFR.
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              Effect of ramipril vs amlodipine on renal outcomes in hypertensive nephrosclerosis: a randomized controlled trial.

              Incidence of end-stage renal disease due to hypertension has increased in recent decades, but the optimal strategy for treatment of hypertension to prevent renal failure is unknown, especially among African Americans. To compare the effects of an angiotensin-converting enzyme (ACE) inhibitor (ramipril), a dihydropyridine calcium channel blocker (amlodipine), and a beta-blocker (metoprolol) on hypertensive renal disease progression. Interim analysis of a randomized, double-blind, 3 x 2 factorial trial conducted in 1094 African Americans aged 18 to 70 years with hypertensive renal disease (glomerular filtration rate [GFR] of 20-65 mL/min per 1.73 m(2)) enrolled between February 1995 and September 1998. This report compares the ramipril and amlodipine groups following discontinuation of the amlodipine intervention in September 2000. Participants were randomly assigned to receive amlodipine, 5 to 10 mg/d (n = 217), ramipril, 2.5 to 10 mg/d (n = 436), or metoprolol, 50 to 200 mg/d (n = 441), with other agents added to achieve 1 of 2 blood pressure goals. The primary outcome measure was the rate of change in GFR; the main secondary outcome was a composite index of the clinical end points of reduction in GFR of more than 50% or 25 mL/min per 1.73 m(2), end-stage renal disease, or death. Among participants with a urinary protein to creatinine ratio of >0.22 (corresponding approximately to proteinuria of more than 300 mg/d), the ramipril group had a 36% (2.02 [SE, 0.74] mL/min per 1.73 m(2)/y) slower mean decline in GFR over 3 years (P =.006) and a 48% reduced risk of the clinical end points vs the amlodipine group (95% confidence interval [CI], 20%-66%). In the entire cohort, there was no significant difference in mean GFR decline from baseline to 3 years between treatment groups (P =.38). However, compared with the amlodipine group, after adjustment for baseline covariates the ramipril group had a 38% reduced risk of clinical end points (95% CI, 13%-56%), a 36% slower mean decline in GFR after 3 months (P =.002), and less proteinuria (P<.001). Ramipril, compared with amlodipine, retards renal disease progression in patients with hypertensive renal disease and proteinuria and may offer benefit to patients without proteinuria.
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                Author and article information

                Contributors
                zxhzpp@hotmail.com
                Rule.Andrew@mayo.edu
                Charles.McCulloch@ucsf.edu
                Lieske.John@mayo.edu
                Elaine.Ku@ucsf.edu
                Chi-yuan.Hsu@ucsf.edu
                Journal
                BMC Nephrol
                BMC Nephrol
                BMC Nephrology
                BioMed Central (London )
                1471-2369
                30 March 2020
                30 March 2020
                2020
                : 21
                : 108
                Affiliations
                [1 ]GRID grid.413106.1, ISNI 0000 0000 9889 6335, Department of Health Care, , Peking Union Medical College Hospital, Chinese Academy of Medical Science & Peking Union Medical College, ; No. 1, Shuaifuyuan, Wangfujing St., Beijing, 100730 China
                [2 ]GRID grid.66875.3a, ISNI 0000 0004 0459 167X, Division of Nephrology and Hypertension, , Mayo Clinic, ; Rochester, MN USA
                [3 ]GRID grid.66875.3a, ISNI 0000 0004 0459 167X, Division of Epidemiology, , Mayo Clinic, ; Rochester, MN USA
                [4 ]GRID grid.66875.3a, ISNI 0000 0004 0459 167X, Department of Laboratory Medicine and Pathology, , Mayo Clinic, ; Rochester, MN USA
                [5 ]GRID grid.266102.1, ISNI 0000 0001 2297 6811, Division of Biostatistics, Department of Epidemiology and Biostatistics, , University of California, San Francisco, ; San Francisco, CA USA
                [6 ]GRID grid.266102.1, ISNI 0000 0001 2297 6811, Division of Nephrology, , University of California, San Francisco, ; San Francisco, CA USA
                Article
                1736
                10.1186/s12882-020-01736-6
                7104490
                32228497
                769d0b66-bd37-4b5f-99d7-28c8dce7fd21
                © The Author(s) 2020

                Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

                History
                : 8 March 2019
                : 21 February 2020
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/100000062, National Institute of Diabetes and Digestive and Kidney Diseases;
                Award ID: K24 DK92291
                Award ID: R01 DK090358
                Award Recipient :
                Categories
                Research Article
                Custom metadata
                © The Author(s) 2020

                Nephrology
                chronic kidney disease (ckd),glomerular filtration rate (gfr),measurement error,tubular secretion of creatinine,creatinine clearance (crcl)

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