VLD 421: Veterinary Clinical Biochemistry and Laboratory Diagnosis-II (0+1)

Estimation of Creatinine

METHOD OF ESTIMATION - ALKALINE PICRATE METHOD

• Alkaline picrate method is used to estimate the creatinine concentration in serum. But it measures some non-creatinine chromogens present in plasma. It can be rectified by using Lloyd’s reagent, which measures only the true creatinine.

Principle

• Creatinine reacts with the picric acid to produce a colored compound, creatinine alkaline picrate. The change in absorbance is proportional to creatinine concentration.

Reagents composition

• Creatinine dye reagent
  • Picric acid - 8.73 mmol/L
  • Surfactant
• Creatinine base reagent
  • Sodium hydroxide - 300 mmol/L
  • Sodium phosphate - 25 mmol/Lab

Laboratory procedure

	Standard	Sample
Working reagent	1000 µL	1000 µL
Standard	100 µL	-
Sample	-	100 µL
Mix and read the optical density (T1) 6 seconds after the sample or standard addition. Exactly after 6 seconds after the first reading take second reading (T2).

Caculation

Creatinine conc. (mg/dL) = ( T₂ – T₁) of sample) / (T₂ – T₁) of   standard ) X 2