Creatinine Flashcards
who described the method for the determination of creatinine involving a protein-free filtrate and reaction with picric acid in an alkaline solution.
Jaffe (1886)
interferences of creatinine
protein and glucose
Kinetic procedures have become popular because they are __, ___, ____
rapid
simple
avoid interference
The present method is based on a modification of the automated reaction rate of ____ and _____.
Fabinay and Eringshausen
Principle of Creatinine
Creatinine + Picric Acid —> Creatine-picrate complex
reagent preparation
1 part of creatinine acid
! part of creatinine base
working reagent is stable for ___ days, ___°C
30 days, 15-30°C
Creatinine Acid Reagent =
Creatinine Base Reagent =
Creatinine Standard =
Aqueous solution of picric acid
Aqueous solution of sodium hydroxide
Aqueous solution of creatinine zinc chloride.
sample stability
1 day = 2-8°C
months = -20°C
preservation of urine
15 grams boric acid = 4-7 days RT (15-25°C)
specimen used
Serum
urine: 24-hour urine (1:20 (1+19))
wavelength used
510 nanometer
reaction type
kinetic
creatinine came from
kidneys, muscles
Formula
serum: au/as x 5
Urine: au/as x 5x 20
procedure
Manual Procedure
1. Set spectrophotometer cuvette temperature to 37°C.
2. Zero spectrophotometer with D.I. water at 510 nm.
3. Pipet 1.0 mL of working reagent into test tubes and prewarm at 37°C for 3 minutes.
4. Transfer 0.050 mL (50 µL) of standard to test tube, mix, and immediately place in cuvette well.
5. After exactly twenty (20) seconds read and record absorbance (A1).
6. At exactly sixty (60) seconds after reading (A1), read and record absorbance (A2).
7. Calculate the change in absorbance (∆A) by subtracting (A2-A1).
Normal Range:
Male (serum): 0.9 - 1.5 mg/dL
Male (urine): 1000 - 2000 mg/24hrs.
Female (serum): 0.7 - 1.4 mg/dL
Female (urine): 600 - 1500 mg/24hrs.
