Estimated GFR vs Creatinine Clearance for Drug Dosing (MDRD) Study equation for estimated glomerular filtration rate (GFR) is an acceptable AGREEMENT BETWEEN KIDNEY FUNCTION ESTIMATES FOR DRUG Advertisements on this site do not constitute a guarantee or endorsement by the journal, Association. The kidneys' ability to handle creatinine is called the creatinine clearance rate, which helps to estimate the glomerular filtration rate (GFR) -- the. Scott Med J. Nov;51(4) The relationship between serum creatinine and estimated glomerular filtration rate: implications for clinical practice. Nelson.
The vital evidence underlying our negative perception of serum creatinine, however, is the data reported by Shemesh et al. The pressure to change to new serum biomarkers of GFR becomes ever more vocal.
Serum Creatinine and Glomerular Filtration Rate: Perception and Reality | Clinical Chemistry
Formal GFR was measured by iohexol clearance. The authors provide a detailed discussion of the limitations of their study, but their conclusions that the 3 biomarkers are equivalent, both in terms of diagnostic performance—even for minor degrees of deterioration of renal function—and in terms of risk prediction for progression, should help to improve our perception of serum creatinine.
Any serum biomarker of GFR must obey the laws of physics: As the GFR declines, the serum concentration should increase. The fact that the relationship between serum concentration and GFR is a reciprocal function explains how the relatively small changes in concentration that occur in the early stages of renal function decline are followed by an accelerating increase.
Consequently, for decades nephrologists in clinical practice have monitored the rate of progression of renal disease in patients by simply plotting the reciprocal of the serum creatinine concentration against time.How To Read Kidney Blood Test Result (GFR, Creatinine, Creatinine Clearance Test, Potassium Sodium)
This reciprocal function is not unique to creatinine but is true for any biomarker of GFR. The physics is confirmed by Spanaus et al. Further exploration of the discrepancy between our perception of serum creatinine and the conclusions of Spanaus et al.
Publications promoting new serum biomarkers of GFR have tended to use ROC curve analysis to demonstrate better, usually only marginally, diagnostic performance; however, diagnosis represents only one of the clinical applications of measuring serum creatinine. A clinically crucial situation in which creatinine is considered both diagnostically sensitive and reliable is the monitoring of graft function after renal transplantation, for which alterations in the dosing of immunosuppressive drugs are based on small changes in the serum creatinine concentration, usually within the reference interval.
The explanation for the contradiction to our perception lies in an understanding of biological variation, a fundamental concept in clinical chemistry.
The implicit conclusions are that applying a reference interval for serum creatinine is inappropriate, thereby resolving the apparent incongruity of the Shemesh data 12and that longitudinal monitoring of serum creatinine in any individual will ensure early detection of GFR decline and incipient renal disease.
Distribution of animal on basis of creatinine range and mean GFR and mean serum creatinine Table 2: Statistical analysis of the creatinine and GFR relationship Interindividual variations was observed in 5 False negative observations were seen in two 4.
The pattern of curve has several consequences.
Serum Creatinine and Glomerular Filtration Rate: Perception and Reality
At both ends, a large variation of one parameter corresponds to a very small change in the other which means that a reduction of GFR has modest effect on serum creatinine and a huge decrease of creatinine corresponds to only a minor increase in GFR, therefore in early stages of renal disease, these tests could create a false sense of security.
These which observations are in agreement with Finco et al. Serum creatinine is also an unreliable indicator of renal function and often overestimates GFR in chronic renal failure.
Interindividual variations were observed in In such dogs creatinine was found a poor predictor of change in GFR. The findings are in agreement with Finco et al. In two dogs, creatinine was within normal range but there was decrease in GFR on scintigraphic analysis, the suggested reason for this observation is presentation of dogs in phase of early renal failure, this observation is in accordance with Bauer et al.
In four dogs, normal GFR with marginally high creatinine values was observed, the possible cause for this may be the diet of dogs as reported by Watson et al.
In this study both kenneled dogs and stray dogs were included, that may be another possible cause of interindividual variation as reported by Rautenbach and Joubert who found a higher creatinine in dogs living outside than in kenneled dogs, although their weight and food intake were similar. Also usefulness of creatinine estimation is limited in early renal failure when marked reduction of GFR may be associated with little change in creatinine concentration, therefore serum creatinine should only be used for screening of animal for renal diseases, monitoring the progression of renal disease or the efficiency of a treatment.
In contrast, scintigraphy has the advantage of physiological imaging and can be used in early diagnosis of renal failure in dogs to enable timely application of therapeutic intervention.
This imaging technique has added advantage of estimating global and individual kidney function which can not be obtained by creatinine estimation. Renal function studies in man with advanced renal insufficiency.
Outline of Veterinary Clinical Pathology.
Standardized serum creatinine measurements are critical to reducing variability in calculated GFR and to ongoing global public health efforts to increase the diagnosis and treatment of chronic kidney disease. Standardizing calibration of creatinine results to an isotope dilution mass spectrometry reference measurement procedure requires coordination by method manufacturers and clinical laboratories to use the correct MRDR equation to calculate GFR and to communicate associated clinical issues to care providers and pharmacists.
The program promotes public awareness for early detection and treatment of kidney disease to prevent or slow disease progression. The program was initiated because kidney failure is an important public health problem and the incidence of kidney failure and chronic kidney disease CKD has risen dramatically in the last 20 years .
Reporting calculated GFR from serum creatinine
Glomerular filtration rate GFR is considered the best overall indicator of kidney function. GFR is difficult to measure directly and various procedures to estimate GFR from other laboratory tests have been used.
Creatinine is a commonly measured laboratory test and the other demographic parameters are readily available. MDRD equation, IDMS traceable The MDRD equation has shown good performance for patients with diabetic nephropathy  and less satisfactory performance for sick inpatients  and for people with near-normal renal function .
Validation studies are in progress to include additional ethnic groups and to evaluate alternate estimating equations. Because the relationship between serum creatinine and GFR is difficult to interpret, particularly at the low creatinine concentrations that correspond to early CKD, the NKDEP recommends that a calculated GFR be reported with all serum creatinine measurements.
This strategy will enable identification of patients early in the course of their kidney disease when therapy can be applied to reduce the progression of CKD and delay or prevent end-stage renal failure. A Laboratory Working Group was formed to address the issues of variability in creatinine measurement and to develop a standardization program to reduce the impact of creatinine variability on the utility of the calculated GFR.
The laboratory working group includes global membership and cooperative relationships with professional organizations from other countries. Variability in measurement of creatinine 0. As the GFR decreases, the creatinine concentration increases, and the relative impact of bias and imprecision on the estimated GFR becomes less significant. The NKDEP Laboratory Working Group has developed a standardization program for serum creatinine measurements to reduce the bias of creatinine measurements that will, in turn, improve the accuracy and consistency of calculated GFR values.
All methods for measuring serum creatinine should have calibration traceable to an isotope dilution mass spectrometry IDMS reference measurement procedure.