Serum Creatinine Flashcards
Reaction principle
Creatinine + picric acid —> creatinine-picrate complex
Basis of serum creatinine measurement
Kinetic Jaffe reaction
Contents
PIC
NaOH
Standard creatinine
Complex produced when creatinine in alkaline solution is added with picric acid
Orange-colored
Proportional to the creatinine concentration in the sample
Absorbance of complex
Specimen
1 Serum (or heparinized plasma) Stability: 24 hours at 2 Celsius to 8 Celsius 2 Urine (diluted in the ratio 1 + 49)
Reagent stability
1 Expiry date (reagent/diluted sodium hydroxide when stored at 15-25 Celsius)
2 4 weeks (working reagent protected from light)
Reagent preparation
1 For measurement at 25 Celsius, dilute NaOH with distilled water in the ratio 1+4
2 For measurement at 37 Celsius, dilute NaOH with distilled water in the ratio 1+7
Wavelength
492 nm (490-510 nm)
Optical path
1 cm
Temperature
25/37 Celsius
Measurement
Against air (increasing absorbance)
Calculation of serum creatinine concentration
1 C = 2.0 x (sample absorbance/standard absorbance) (mg/dL)
2 C = 176.8 x (sample absorbance/standard absorbance) (mmol/L)
Calculation of urine creatinine concentration
C = 100 x (sample absorbance/standard absorbance) (mg/dL)
Reference range
Male 1 Conventional (mg/dL) = 0.6-1.1 2 SI (mmol/L) = 53-97
Female 1 Conventional (mg/dL) = 0.5-0.9 2 SI (mmol/L) = 44-80
