Fulltext - Relationship of Serum Creatinine and Glomerular Filtration Rate by 99mTc-DTPA Scintigraphy in Dogs with Renal Failure. In view of this relationship to muscular mass, serum creatinine concentration and . Estimation of glomerular filtration rate by creatinine-based formulas: Any. for the estimation of glomerular filtration rate (GFR). They are organized into 5) What is the difference between creatinine clearance and GFR? 6) What is the.
Serum Creatinine and Glomerular Filtration Rate: Perception and Reality
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.
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.
This example of truly personalized medicine in which reference intervals do not apply is applicable only when the biological variation of the analyte is low and analytical methods with the appropriate imprecision are available. Unfortunately, this simple truth is not universally appreciated.Renal Clearance, Renal Plasma Flow and Glomerular Filtration Rate
The true clinical value of serum creatinine is its diagnostic sensitivity in detecting small changes in GFR. Consequently, the use of cystatin C to monitor renal function in an individual, particularly in the early stages of kidney disease or after transplantation, is not valid.
It can be used to evaluate the posttransplantation GFR 16 but not the small changes that will determine adjustments to immunosuppressive therapy. Serum creatinine is not a perfect biomarker of GFR. Tubular secretion, an altered production rate, and analytical specificity mean that it is not applicable in all clinical situations, and interpretation often remains an art.
The professional perception that serum creatinine is an insensitive biomarker of early changes in GFR is totally incorrect. The data presented by Spanaus et al.
The reality is that serum creatinine is still a very good measure of GFR and is by far the most sensitive serum biomarker for detecting small GFR changes in an individual. All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: Under steady state conditions, the rate of creatinine excretion is equal to the rate of its production in skeletal muscles which Guyton and Hall,so its measurement indirectly reflects the GFR.
The determination of GFR is especially valuable as it can detect renal dysfunction in patients Ettinger et al. Gamma camera technique is the only method to determine GFR, both as a global value of enal function and as an individual function of each kidney Kampa, This agent is excreted principally by kidney and can be used to measure GFR; accumulation by the kidneys reflects reduced renal function.
The agent can also be used to assess renal blood flow, suspected renovascular hypertension and obstructive uropathy ACR practice guideline, ACR Present communication reports a relationship between serum creatinine and glomerular filtration rate in dogs suffering from renal failure. The study was performed on 44 canine patients with renal disorder referred from Bai Sakarabai Dinshaw Pettit Hospital for Animals affiliated from Bombay Veterinary college.
A total of 44 dogs of either sex, breed weighing about The inclusive criterion for the dogs was serum creatinine level more than 2. All the dogs underwent routine hematology and serum biochemistry analysis along with electrolyte analysis as per standard procedure suggested by Benjamin Based on clinical examination and findings of Packed Cell Volume and urine specific gravity, best possible oral hydration done approximately 2 h prior to the study as state of hydration has been reported to affect the Glomerular Filteration Rate Kampa, After oral rehydration, if required, intravenous hydration was also done using normal saline 15 mL kg-1 body weight over a period of 30 min before the study.
Scintigraphy was performed using 6. Curvilinear relationship between GFR and serum creatinine Counting of activity in front of the gamma camera before and after injection and correction for radioactive decay during the time interval was done.
A dynamic acquisition was started of six frames per minute for 20 min. A low energy all purpose LEGP collimator on a gamma camera was used and 64x64 pixel matrix for the dynamic study and x matrix was selected for static study.
Immediately after the dynamic acquisition period, the camera was rotated 90 degree above the dog and a static lateral 30 sec image was made to measure the kidney depth.
Serum Creatinine and Glomerular Filtration Rate: Perception and Reality | Clinical Chemistry
The camera was then returned to its original position and the activity in the syringe was counted to exclude it from injected dose. Gates Analysis programming was used to generate time activity curve. For correction of background activity, small crescent shape areas were manually drawn at the caudal pole of the kidneys Liedtke and Duarte, Serum creatinine is used as screening test of renal function as it is handled primarily by glomerular filtration and essentially reflects GFR.
Maximum observed GFR was 4. In our study 38 dogs 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. 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.