eGFR Threshold Research Articles

Arterial spin labeling MRI for assessment of perfusion in native and transplanted kidneys

PurposeTo apply a magnetic resonance arterial spin labeling (ASL) technique to evaluate kidney perfusion in native and transplanted kidneys. Materials and MethodsThis study was compliant with the Health Insurance Portability and Accountability Act and approved by the institutional review board. Informed consent was obtained from all subjects. Renal perfusion exams were performed at 1.5 T in a total of 25 subjects: 10 with native and 15 with transplanted kidneys. A flow-sensitive alternating inversion recovery (FAIR) ASL sequence was performed with respiratory triggering in all subjects and under free-breathing conditions in five transplant subjects. Thirty-two control/tag pairs were acquired and processed using a single-compartment model. Perfusion in native and transplanted kidneys was compared above and below an estimated glomerular filtration rate (eGFR) threshold of 60 ml/min per 1.73 m2 and correlations with eGFR were determined. ResultsIn many of the transplanted kidneys, major feeding vessels in the coronal plane required a slice orientation sagittal to the kidney. Renal motion during the examination was observed in native and transplant subjects and was corrected with registration. Cortical perfusion correlated with eGFR in native (r=0.85, P=.002) and transplant subjects (r=0.61, P=.02). For subjects with eGFR >60 ml/min per 1.73 m2, native kidneys demonstrated greater cortical (P=.01) and medullary (P=.04) perfusion than transplanted kidneys. For subjects with eGFR <60 ml/min per 1.73 m2, native kidneys demonstrated greater medullary perfusion (P=.04) compared to transplanted kidneys. Free-breathing acquisitions provided renal perfusion measurements that were slightly lower compared to the coached/triggered technique, although no statistical differences were observed. ConclusionIn conclusion, FAIR-ASL was able to measure renal perfusion in subjects with native and transplanted kidneys, potentially providing a clinically viable technique for monitoring kidney function.

Cum Hoc, Ergo Propter Hoc

In the November 2008 issue of CJASN , Ibrahim et al. (1) reported racial differences in metabolic characteristics of the National Health and Nutrition Examination Survey (NHANES) 2003 through 2006 population with respect the presence or absence of chronic kidney disease (CKD) defined by an estimated GFR (eGFR) > and <60 ml/min. The authors concluded that the African American population is more likely to experience metabolic consequences of CKD before reaching the eGFR <60 ml/min threshold and asserted that these observations support a need to adapt clinical practice guidelines shifting screening for CKD to a higher eGFR threshold specifically for African Americans. These same contentions were made by four of the five authors in an article published only months earlier in JASN (1,2). The assumption that the measured clinical parameters in this representative population are physiologically linked to CKD in African Americans is simplistic and ignores the effects of a combination of genetic and physiologic adaptations superimposed on a background of social and environmental factors that account for minority health disparities (3). The observed population differences noted in the article by Ibrahim et al. (1) were previously well described and should not serve as justification for the policy changes that the authors recommend. Although we agree that clinical practice guidelines should be reviewed and refined over time, the contention that the prevalence or severity of hypertension, …

RIFLE is not RIFLE: on the comparability of results

In the consensus RIFLE criteria [1] of acute kidney injury (AKI) the thresholds given for serum creatinine (sCr) increase and glomerular filtration rate (GFR) decrease (Table ​(Table1)1) do not correspond [2]. Direct measurement of GFR in clinical practice is difficult, and values are more often estimated (eGFR) by the Cockroft-Gault equation or the Modification of Diet in Renal Disease (MDRD) formula. In addition, there is controversy in the literature whether eGFR provides more clinical information regarding AKI than changes in sCr [3]. Table 1 RIFLE criteria for the definition of acute kidney injury (urinary output criteria not listed) As an example of the possible discrepancy, a 1.5-fold increase (50%) in sCr from a baseline of 1.0 mg/dL in a 60-year-old white male corresponds to only a 37% eGFR decrease using the MDRD formula. In this scenario the patient is classified in RIFLE class R by both methods. In the same patient an only 30% increase in sCr (1.0 mg/dL to 1.3 mg/dL), however, corresponds to a 26% decrease of eGFR. Therefore, the patient would consequently be classified as having AKI in RIFLE class R by the GFR threshold but not based on sCr changes. This theoretical disagreement in defining and staging AKI by RIFLE has been outlined previously [2], but data to estimate potential discrepancy in a 'real world' scenario are not available. Furthermore, the use of different versions of RIFLE criteria counteracts the original goal of a consensus definition and hinders comparability. To understand the differences better, we applied these two methods of calculating RIFLE to consecutive patients undergoing cardiac surgery with cardiopulmonary bypass between 2005 and 2007 at our institution. AKI was defined by using either largest sCr increase or eGFR decrease (MDRD formula) within the first postoperative week compared to baseline. In all patients a preoperative baseline sCr was available. We did not use urine output criteria to define AKI. Among the total cohort, 9.3% patients were diagnosed as having AKI by the sCr criteria versus 18.9% with eGFR criteria (Table ​(Table2).2). The largest disagreement was detected in class R. Overall, the diagnosis of AKI using eGFR thresholds was more sensitive than sCr changes, and this was also true for staging of patients in RIFLE classes R and I. However, for patients staged in the highest AKI class F, sensitivity was higher for sCr criteria. These discrepancies can be expected to be found in other patient populations when non-uniform methods of determining RIFLE criteria are utilized. Our findings may assist in interpretation of other clinical studies. Table 2 RIFLE classes by creatinine and estimated glomerular filtration rate thresholds Recently the RIFLE criteria have been modified by the Acute Kidney Injury Network (AKIN) [4], and the change in eGFR is no longer included in this consensus definition set. RIFLE criteria calculated by both methods remain widely used and the process of comparison between the two definition schemes (RIFLE and AKIN) in various patient populations is not yet complete. Further validation is required and modifications in the definition and staging of AKI can be expected [5].

Screening for Chronic Kidney Disease Complications in US Adults

An ideal and effective screening tool should perform equally across ethnic groups. The objective of this study was to determine whether the widely advocated creatinine-based estimated GFR (eGFR) threshold of 60 ml/min per 1.73 m(2) identifies the typical metabolic abnormalities related to chronic kidney disease equally well in minority and nonminority adults. This objective was addressed using data for 8918 minority and nonminority adult participants in the National Health and Nutrition Examination Survey 2003 through 2006, which used stratified, multistage, probability sampling methods to assemble a nationwide probability sample of the noninstitutionalized population of the United States. Metabolic abnormalities including BP, potassium, hemoglobin, bicarbonate, uric acid, calcium, phosphorus, and parathyroid hormone were defined by fifth or 95th percentile values. Among participants with eGFR <60 ml/min per 1.73 m(2), black individuals were more likely than white individuals to have low hemoglobin (adjusted odds ratio [aOR] 3.76; 95% confidence interval [CI] 1.94 to 7.28), elevated uric acid (aOR 2.15; 95% CI 1.26 to 3.68), and elevated parathyroid hormone (aOR 3.93; 95% CI 2.33 to 6.66). Metabolic consequences of reduced eGFR are more common in black individuals and seem to be present at levels well above 60 ml/min per 1.73 m(2); thus, black individuals should be screened for the metabolic complications of chronic kidney at higher GFR levels.

Classification of renal disease status using estimated glomerular filtration rates in diabetes

AbstractThe need for the incorporation of estimated glomerular filtration rates (eGFR) in diabetes renal risk assessment is increasingly recognised but the choice of equation to use is not clear. We evaluated the differential impact of eGFR, using the Cockcroft's &amp; Gault's (C&amp;G) and the Modification of Diet in Renal Disease (MDRD) study equations, on the prevalence of various stages of chronic renal disease in our diabetes population.A cross sectional evaluation was conducted amongst 4548 individuals who attended our centre over an 18‐month period. SPSS was utilised for statistical analysis.Of 4171 with complete data, the prevalence of individuals with eGFR &gt;90, 90–60, 60–30 and &lt;30ml/min/1.73m2 were 25%, 46%, 27% and 2% respectively using the C&amp;G equation and 9%, 62%, 27% and 2% respectively using the MDRD equation. The two equations were fully concordant in their classification of eGFR rank in 65%; in 20% of the cohort, the equations were discordant but not at an arbitrary eGFR threshold of 60ml/min/1.73m2; while in 15% of the population the two equations were discordant even at the threshold of 60ml/min/1.73m2, the majority of whom had normal values of serum creatinine and urine albumin:creatinine ratio.In conclusion, the prevalence of various stages of chronic renal disease in our diabetes cohort differed depending on the eGFR equation used, potentially impacting on service provision. To aid clarity and uniformity of practice, there is a need for organisations to decide on a single equation of choice before recommending it to routine diabetes care providers. Copyright © 2007 John Wiley &amp; Sons.

Introducing estimated glomerular filtration rate (eGFR) into clinical practice in the UK: implications for the use of metformin

The reporting of estimated glomerular filtration rate (eGFR) will identify people with diabetes who have previously undiagnosed renal impairment. Our current guideline recommends discontinuation of metformin when serum creatinine > 150 micromol/l. We examined the implications of replacing this with a criterion based on eGFR. The Lothian diabetes register was used to identify patients with Type 2 diabetes for whom age, sex and creatinine measurements within the last 15 months were available. eGFR was calculated using the abbreviated Modification of Diet in Renal Disease (MDRD) equation. Of 19,981 patients with Type 2 diabetes, 11,297 were taking metformin in accordance with our current guideline. Of these, 9259 (82.0%) had at least stage 2 renal impairment (eGFR < 90 ml/min per 1.73 m(2)) and 2880 (25.5%) had at least stage 3 renal impairment (eGFR < 60 ml/min per 1.73 m(2)). Changing to an eGFR threshold of 36 ml/min per 1.73 m(2) would have a neutral effect on the number of patients eligible for metformin therapy and would permit its use in patients with creatinine concentrations as high as 179 micromol/l. An eGFR threshold of 40 ml/min per 1.73 m(2) would result in 312 (2.8%) patients discontinuing metformin and would permit metformin to be used with creatinine concentrations as high as 163 micromol/l. The introduction of eGFR reporting could have a major effect on prescription of metformin. A threshold eGFR of 36-40 ml/min per 1.73 m(2) is approximately consistent with our current practice. If our current practice is considered safe, this would be a useful recommendation.