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Lab (5): Renal Function test (RFT) (Part 2) T.A Nouf Alshareef T.A Bahiya Osrah KAU-Faculty of Science- Biochemistry department Clinical biochemistry lab (Bioc 416) 2012 Creatinine • Creatinine is by-product of muscle energy metabolism that it is a waste product and filtered from the blood by kidneys and then excreted into the urine. • Production of creatinine depends on an individual's muscle mass, which is usually constant. • Its level considered a sensitive renal function marker. Serum creatinine: • In renal failure, the level of creatinine is elevated in blood and decreased in urine because kidney unable to excrete creatinine in urine. • Elevated blood creatinine is a more sensitive indication of impaired kidney function than the BUN: Its level only effected by muscle mass which is usually constant creatinine level is very little affected by liver function Comparison between BUN & Creatinine • Blood urea level is sensitive but not specific indicator for renal dysfunction, because: Its level is affected by dietary protein Other non renal causes such as liver disease and blood pressure may raise its level. Its level is elevated in last stages of renal failure after 50% of renal function is lost. • Elevated blood creatinine is a more sensitive indication of impaired kidney function than the BUN: Its level only effected by muscle mass which is usually constant creatinine level is very little affected by liver function BUN/Creatinine ratio: - BUN-creatinine ratios increase with renal disease. - effected by other factors as: liver function, muscle mass, dietary protein High BUN-to-creatinine ratio: Low BUN-to-creatinine ratio: • Sudden acute kidney failure. • Low protein diet • Urinary tract blockage (kidney stone). • Severe muscle injury. • Very high ratio may be caused by bleeding in the digestive tract or respiratory tract. Glomerular Filtration Rate (GFR): • is the rate (volume per minute) at which the filtration of blood blood is performed by the glomerulus and transferred to Bowman's space. • It is determined practically by measuring creatinie clearance. Creatinine clearance: • is the volume of blood plasma that is cleared of creatinine per unit time (expressed in ml/min). • It measures GFR • Normal range: man: 120ml/min women:100ml/min If GFR less than 60 ml/min: for 3 months the patient has chronic kidney disease CKD. If GFR is less than 10 ml/min: this stage is called end-stage kidney disease or end-stage renal disease (ESRD). • End stage means kidneys can’t filter chemicals and minerals out of blood. • In this stage patient needs dialysis or kidney transplant. According to the value of GFR, kidney disease is classified to five stages: Stage of kidney disease 1 2 3 4 5 Normal Mild reduced Moderately reduced severely reduced Kidney failure 120 90 30 10 60 Glomerular Filtration Rate (approximate percent of kidney failuar) Creatinine clearance calculation: • can be calculated without a 24 hour urine collection using: • serum creatinine concentration • sex, age, and weight Cockroft equation: (Weight in Kg, creatinine in μmol/L, constant: men = 1.23, women= 1.04) Principle: Alkaline • The rate of formation of colored complex is directly related to creatinine conc. Kit components Sample: • Serum or urine Procedure: Calculations Normal Range Can you calculate creatinine clearance ??? Creatinine clearance Weight in Kg, creatinine in μmol/L, constant: men = 1.23, women= 1.04) Stage of kidney disease Stage of kidney disease 1 2 3 4 5 Normal Mild reduced Moderately reduced severely reduced Kidney failure 120 90 30 10 60 Glomerular Filtration Rate (approximate percent of kidney failuar)