Store at 2-8ºC
PRINCIPLE OF THE METHOD
The assay is based on the reaction of creatinine with sodium picrate as
described by Jaffé.
Creatinine reacts with alkaline picrate forming a red complex. The time
interval chosen for measurements avoids interferences from other
serum constituents.
The intensity of the color formed is proportional to the creatinine
concentration in the sample1.
CLINICAL SIGNIFICANCE
Creatinine is the result of the degradation of the creatine, component
of muscles, it can be transformed into ATP, that is a source of high
energy for the cells. The creatinine production depends on the
modification of the muscular mass, and it varies little and the levels
usually are very stable.
Is excreted by the kidneys. With progressive renal insufficiency there is
retention in blood of urea, creatinine and uric acid.
Elevate creatinine level may be indicative of renal insufficiency1,4,5.
Clinical diagnosis should not be made on a single test result; it should
integrate clinical and other laboratory data.
STORAGE AND STABILITY
All the components of the kit are stable until the expiration date on the
label when stored tightly closed at 2-8ºC, protected from light and
contaminations prevented during their use.
Do not use reagents over the expiration date.
Signs of reagent deterioration:
- Presence of particles and turbidity.
- Blank absorbance (A) at 492 nm
1,80.
ADDITIONAL EQUIPMENT
- Spectrophotometer or colorimeter measuring at 492 nm (490-510).
- Matched cuvettes 1,0 cm light path.
- General laboratory equipment.
SAMPLES
- Serum or heparinized plasma1
.
Creatinine stability: 24 hours at 2-8ºC.
- Urine (24 h)1
: Dilute sample 1/50 with distilled water. Mix. Multiply
results by 50 (dilution factor);
Creatinine stability: 7 days at 2-8ºC.
QUALITY CONTROL
Control sera are recommended to monitor the performance of assay
procedures: SPINTROL H Normal and Pathologic (Ref. 1002120 and
1002210).
If control values are found outside the defined range, check the
instrument, reagents and calibrator for problems.
Each laboratory should establish its own Quality Control scheme and
corrective actions if controls do not meet the acceptable tolerances.
NOTES
1. Use clean disposable pipette tips for its dispensation.
2. SPINREACT has instruction sheets for several automatic
analyzers. Instructions for many of them are available on request.
BIBLIOGRAPHY
1. Murray R.L. Creatinine. Kaplan A et al. Clin Chem The C.V. Mosby Co.
St Louis. Toronto. Princeton 1984; 1261-1266 and 418.
2. Young DS. Effects of drugs on Clinical Lab. Tests, 4th ed AACC Press,
1995.
3. Young DS. Effects of disease on Clinical Lab. Tests, 4th ed AACC 2001.
4. Burtis A et al. Tietz Textbook of Clinical Chemistry, 3rd ed AACC 1999.
5. Tietz N W et al. Clinical Guide to Laboratory Tests, 3rd ed AACC 1995.
