Creatinine Blood Test in lab
Kidney Function Panel
Colorimetric Technique (Jaffe’s Method)
Formal name: Creatinine
2) What is the Creatinine?
3) Why it is required?
4) When should you get tested?
5) What are the needed preparations before the test?
1) Sample type:-
2) Sample collection method:-
3) Criteria for sample rejection:-
ِColorimetric-Kinetic technique (IFCC METHOD)
By Spinreact kits
2) Devices used:-
Kits of Creatinine from Spinreact Company with reference code 1001110, 1001111, 1001112, 1001113.
- Reagent 1 (R1) (color reagent): picric acid 17.5 mol/l.
- Reagent 2 (R2) (alkaline sol.): sodium hydroxide 0.29 mmol/l.
- Standard: Creatinine 2mg/dl (177 µmol/l).
- Store at 2-8oC
- Reagents and standards are stable until the expiry date shown on the label when stored tightly closed, protected from light and contaminations prevented during their use.
- Indications of deterioration:
- Reagents:- presence of particles, turbidity and absorbance of the blank over ≥1.80 at 452-510 nm (1 cm cuvette).
- Standard solution:– Presence of particles and turbidity.
- Reagent preparation
- Standard (S):- ready to use
- Working Reagent: Mix equal volumes of R1 and R2. Mix gently (because the cuvette needs 1 ml to be filled, you need to mix at least 500µl R1 with 500µl R2).
- Stable for one month at 2-8ºC.
- Clean the cuvettes or tubes if you use a spectrophotometer or semi-automated analyzer without suction system or flush the aspiration system of your semi-automated analyzer if it is with suction system by keeping the tubing in a distilled water for 2 minutes.
- In a clean tube or directly in the cuvette, Mix equal volumes of the colouring reagent (R1) and the alkaline solution (R2) to make the working solution as instructed by the reagent supplier (500µl R1 with 500µl R2)
- Zero the instrument with reagent blank at 500 nm (because the reagent is not colorless).
- Bring 3 clean tubes; and add the following:
working solution (ml)
- Incubate at 37oC for 2-5 minutes to brink it to 37oC
- Then add the serum and standard as follow:-
|working solution (ml)||1.0||1.0||1.0|
|Sample (ml)||–||0.1 (100µl)||–|
|Standard (ml)||–||–||0.1 (100µl)|
- Start the stopwatch or timer immediately after adding the standard and sample then continue incubation at 37oC.
- Read the absorbance at 500nm after 30 seconds (A1), then wait up to 90 seconds (A2) (i.e. the total time is 90 second) and find the concentration (see the calculations).
Creatinine concentration is calculated from the following equation.
ΔAsample = ΔA1 – ΔA2 and ΔAstandard = ΔA1 – ΔA2
It is better to see the how we get this equation in the calculation section in the general concept part.
It is best to see the calculation part in the general concept. click here
6) Reference range:-
|Men||0.7 – 1.4 mg/dl = 61.8 – 123.7 μmol/l|
|Women||0.6 – 1.1 mg/dl = 53 – 97.2 μmol/LL|
Females have lower creatinine level than men because they have lower muscle mass.