Urea is the final result of the metabolism of proteins; It is formed in the liver
from their destruction.
It can appear the urea elevated in blood (uremia) in: diets with excess of
proteins, renal diseases, heart failure, gastrointestinal hemorrhage,
dehydration or renal obstruction1,4,5
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 340 nm 1.00.
ADDITIONAL EQUIPMENT
- Spectrophotometer or colorimeter measuring at 340 nm.
- Matched cuvettes 1.0 cm light path.
- General laboratory equipment(Note 1)
- SAMPLES
- Serum or heparinized plasma1
: Do not use ammonium salts or fluoride
as anticoagulants.
- Urine1
: Dilute sample 1/50 in distilled water. Mix. Multiply the results by
50 (dilution factor). Preserve urine samples at pH 4.
Urea is stable at 2-8ºC for 5 days.
INTERFERENCES
It is recommended to use heparin as anticoagulant. Do not use ammonium
salts or fluoride1
A list of drugs and other interfering substances with urea determination
has been reported by Young et. al2,3
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,
reagent and calibration for problems.
Each laboratory should establish its own Quality Control scheme and
corrective actions if controls do not meet the acceptable tolerances
NOTES
1. Glassware and distilled water must be free of ammonia and ammonium
salts1
.
2. Use clean disposable pipette tips for its dispensation.
3. SPINREACT has instruction sheets for several automatic analyzers.
Instructions for many of them are available on request.
BIBLIOGRAPHY
1. Kaplan A. Urea. Kaplan A et al. Clin Chem The C.V. Mosby Co. St Louis.
Toronto. Princeton 1984; 1257-1260 and 437 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.
