Practical Bio Chemistry - Determination of Serum Creatinine PDF

Jabir ibn Hayyan University For medical &Pharmaceutical Science Medicine collage Chemistry and Biochemistry Branch PRACTICAL BIO CHEMISTRY DETERMINATION OF SERUM CREATININE  DR.HAZIM / M.SC. ALI MOHAMMAD Practical bio Chemistry sophomore Dr.Hazim almusaw...

Jabir ibn Hayyan University For medical &Pharmaceutical Science Medicine collage Chemistry and Biochemistry Branch PRACTICAL BIO CHEMISTRY DETERMINATION OF SERUM CREATININE  DR.HAZIM / M.SC. ALI MOHAMMAD Practical bio Chemistry sophomore Dr.Hazim almusawi/M.sc.ali Creatinine (from the Greek κρέας, flesh) is a break-down product of creatine phosphate in muscle, and is usually produced at a fairly constant rate by the body (depending on muscle mass). In chemical terms, creatinine is a spontaneously formed cyclic derivative of creatine. Creatinine is chiefly filtered out of the blood by the kidneys (glomerular filtration and proximal tubular secretion). There is little-to-no tubular reabsorption of creatinine. If the filtering of the kidney is deficient, creatinine blood levels rise. Therefore, creatinine levels in blood and urine may be used to calculate the creatinine clearance (CrCl), which reflects the glomerular filtration rate (GFR). The GFR is clinically important because it is a measurement of renal function. However, in cases of severe renal dysfunction, the creatinine clearance rate will be "overestimated" because the active secretion of creatinine will account for a larger fraction of the total creatinine cleared. Ketoacidosis, cimetidine and trimethoprim reduce creatinine tubular secretion and therefore increase the accuracy of the GFR estimate, particularly in severe renal dysfunction. (In the absence of secretion, creatinine behaves like insulin.) A more complete estimation of renal function can be made when interpreting the blood (plasma) concentration of creatinine along with that of urea. BUN-to-creatinine ratio (the ratio of blood urea nitrogen to creatinine) can indicate other problems besides those intrinsic to the kidney; for example, a urea level raised out of proportion to the creatinine may indicate a pre-renal problem such as volume depletion. Men tend to have higher levels of creatinine because they, in general, have more skeletal muscle mass than women. Vegetarians have been shown to have lower creatinine levels. 1 Practical bio Chemistry sophomore Dr.Hazim almusawi/M.sc.ali Plasma creatinine Measuring serum creatinine is a simple test and it is the most commonly used indicator of renal function. A rise in blood creatinine level is observed only with marked damage to functioning nephrons. Therefore, this test is not suitable for detecting early-stage kidney disease. A better estimation of kidney function is given by the creatinine clearance (CrCl) test. Creatinine clearance can be accurately calculated using serum creatinine concentration and some or all of the following variables: sex, age, weight, and race, as suggested by the American Diabetes Association without a 24-hour urine collection. Some laboratories will calculate the CrCl if written on the pathology request form, and the necessary age, sex, and weight are included in the patient information. Urine creatinine Creatinine concentration is also checked during standard urine drug tests. High creatinine levels indicate a pure test, whereas low amounts of creatinine in the urine indicate a manipulated test, either through the addition of water in the sample or by drinking excessive amounts of water. Creatinine (the creatine anhydride) is synthesized in the liver, kidney and pancreas from 3 amino acids (arginine +glycine +methionine).is a chemical waste molecule that is generated from muscle metabolism as result of creatine metabolism. 1-2% of creatine is spontaneously converted to creatinine daily. Creatinine is one of the most common analyte used as the indicator of glomerular filtration rate (GFR) and kidney function. Creatinine is measured primarily to assess kidney function and has certain advantages over the measurement of urea. The plasma level of creatinine is relatively independent of protein ingestion, water intake, rate of urine production and exercise. Since its rate of production is constant, elevation of plasma creatinine is indicative of under- excretion, suggesting kidney impairment. Depressed levels of plasma creatinine are rare and not clinically significant. 2 Practical bio Chemistry sophomore Dr.Hazim almusawi/M.sc.ali Why is a creatinine blood test done? Doctor may order a creatinine blood test to assess your creatinine levels if show signs of kidney disease. These symptoms include: Fatigue and trouble sleeping A loss of appetite 3 Practical bio Chemistry sophomore Dr.Hazim almusawi/M.sc.ali Swelling in the face, wrists, ankles, or abdomen Lower back pain near the kidneys Changes in urine output and frequency High blood pressure Nausea Vomiting Kidney problems can be related to different diseases or conditions, including: Glomerulonephritis, which is an inflammation of the glomeruli due to damage Pyelonephritis, which is a bacterial infection of the kidneys Prostate disease, such as an enlarged prostate Blockage of the urinary tract, which may be due to kidney stones Decreased blood flow to the kidneys, which may be caused by congestive heart failure, diabetes, or dehydration The death of kidney cells as a result of drug abuse Streptococcal infections, such as post streptococcal glomerulonephritis Creatinine is removed from the blood chiefly by the kidneys, primarily by glomerular filtration, but also by proximal tubular secretion. Little or no tubular reabsorption of creatinine occurs. If the filtration in the kidney is deficient, blood creatinine concentrations rise. Therefore, creatinine concentrations in blood and urine may be used to calculate the creatinine clearance (CrCl), which correlates approximately with the glomerular filtration rate (GFR). Blood creatinine concentrations may also be used alone to calculate the estimated GFR (eGFR). Normal value Male= 0.6-1.2 mg/dL, Female= 0.5-1.0 mg/dL) 4 Practical bio Chemistry sophomore Dr.Hazim almusawi/M.sc.ali Clinical significance: I. Increased: Increased blood creatinine levels occur in the following condition: - A-Impaired renal function. B-Chronic nephritis. C-Obstruction of urinary tract. D-Muscle disease e.g: muscular dystrophy,.poliomyelitis. E-congestive heart failure. F-Shock. G-Dehydration. H-Rhabdomyolysis. II. Decreased level occur in: 1. Small stature. 2. Decreased muscle mass. 3. Advanced and severe liver disease. 4. Pregnancy. Creatinine clearance: The best test to measure the level of kidney function and determine your stage of kidney disease is creatinine clearance. It’s a volume of plasma from which a measured amount of substance can be completely eliminated in to the urine per unit of time. It depends on 1- Plasma concentration and excretory rate 2- Glomerular filtration rate (GFR) 3- Renal plasma flow (RPF) In adults, the normal GFR number is more than 90ml/min. GFR declines with age, even in people without kidney disease to arrive 70ml/min. GFR= Ucr/Scr *UV - Ucr → Urine creatinine - Scr → Serum creatinine - UV → Urine volume expressed in ml/min Principle: Colorimetric reaction (Jaffe reaction) of creatinine with alkaline picrate measured kinetically at 505nm 5 Practical bio Chemistry sophomore Dr.Hazim almusawi/M.sc.ali R1 – piric acid reagent pH=4 R2- Sodium hydroxide R3- Standard solution 2 mg/dl Procedure: Blank Sample Standard Reagent 1 mL 1 mL 1 mL Sample …. 100µL …. Standard …. …. 100µL Mix well. After 30 second read absorbance A1 at 505nm against reagent blank. Exactly 90 second after the first reading record absorbance A2. Calculation: Concentration of serum creatinine = (A2-A1) – AB / (A2-A1) - AB * Concentration of standard 6