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
- Autoanalyzer Spintech 240.
- 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.
REFERENCE VALUES4,5
Serum or plasma:
15-45 mg/dL
2.5-7.5 mmol/L
Urine:
26 – 43 g/24 h
428-714 mmol/24 h
These values are for orientation purpose; each laboratory should
establish its own reference range.
Conversion factor: mg/dL x 0.1665 = mmol/L.
QUALITY CONTROL
Control sera and calibrators are recommended to monitor the
performance of assay procedures: SPINTROL H Calibrator,
SPINTROL H Normal and Pathologic (Ref. 1002011, 1002120 and
1002210).
If control values are found outside the defined range, check the
instrument, reagents and technique 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. Calibration with the aqueous standard may cause a systematic error in
automatic procedures. In these cases, it is recommended to use a
serum Calibrator.
3. Use clean disposable pipette tips for its dispensation.
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 AACC2001.
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.
