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Basis of serum creatinine measurement

Kinetic Jaffe reaction

1

Reaction principle

Creatinine + picric acid ---> creatinine-picrate complex

2

Contents

PIC
NaOH
Standard creatinine

3

Complex produced when creatinine in alkaline solution is added with picric acid

Orange-colored

4

Proportional to the creatinine concentration in the sample

Absorbance of complex

5

Specimen

1 Serum (or heparinized plasma)
Stability: 24 hours at 2 Celsius to 8 Celsius
2 Urine (diluted in the ratio 1 + 49)

6

Reagent stability

1 Expiry date (reagent/diluted sodium hydroxide when stored at 15-25 Celsius)
2 4 weeks (working reagent protected from light)

7

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

8

Wavelength

492 nm (490-510 nm)

9

Optical path

1 cm

10

Temperature

25/37 Celsius

11

Measurement

Against air (increasing absorbance)

12

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)

13

Calculation of urine creatinine concentration

C = 100 x (sample absorbance/standard absorbance) (mg/dL)

14

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

15

T or F. The reaction is highly sensitive to temperature

T

16

Harmful when inhaled, swallowed or in contact with the skin

PIC

17

Affect the assay

Presence of reducing compounds

18

A slight precipitate in this is insignificant

Sodium hydroxide

19

Procedure

1 After mixing the reagent and serum, immediately read the absorbance after 30 seconds
2 After 2 minutes

Absorbance = A2-A1