Store 2 - 8ºC.
PRINCIPLE OF THE METHOD
PRE-ALBUMIN is a quantitative turbidimetric test for the measurement of
prealbumin in human serum or plasma.
Anti-prealbumin antibodies when mixed with samples containing prealbumin,
form insoluble complexes. These complexes cause an absorbance change,
dependent upon the prealbumin concentration of the patient sample, that can
be quantified by comparison from a calibrator of know prealbumin
concentration.
CLINICAL SIGNIFICANCE
The prealbumin is a non-glycosilated protein synthesized mainly in the liver
and choroid plexus of the brain. It binds and transport approximately 10% of
serum thyroxin and triiodothyronine, and also plays a role in the transport of
vitamin A in complex with retinal-binding protein.
Prealbumin is the earliest laboratory indicator of nutritional status and has
emerged as the preferred marker for malnutrition because it correlates with
patient outcomes in wide variety of clinical conditions. It is also a negative
acute phase protein; serum levels falls in inflammation and malignancy, as
well as cirrhosis, protein-losing enteropathy and zinc deficiency. However, the
presence of a prealbumin producing tumor or Hodgkin’s disease will increase
serum concentrations.
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 and contaminations are prevented during
their use. Do not use reagents over the expiration date.
Reagent deterioration: The presence of particles and turbidity.
Do not freeze; frozen Antibody or Diluent could change the functionality
of the test.
ADDITIONAL EQUIPMENT
- Thermostatic bath at 37ºC.
- Spectrophotometer or photometer thermostatable at 37ºC with a 340 nm
filter (320 – 360 nm).
SAMPLES
Fresh serum or plasma. EDTA or heparin should be used as anticoagulant.
Stable 7 days at 2-8ºC or 3 months at –20ºC.
The samples with presence of fibrin should be centrifuged before testing.
Do not use highly hemolized or lipemic samples.
PROCEDURE
1. Bring the reagents and the photometer (cuvette holder) to 37ºC.
2. Assay conditions:
Wavelength: 340 nm
Temperature: 37 ºC
Cuvette ligth path: 1cm
3. Adjust the instrument to zero with distilled water.
4.Pipette into a cuvette:
Reagent R1 (µL) 800
Sample or Calibrator (µL) 10
5. Mix and read the absorbance (A1) after the sample addition.
6.Immediately, pipette into de cuvette:
Reagent R2 (µL) 200
7. Mix and read the absorbance (A2) of calibrators and sample exactly 2
minutes after the R2 addition.
Spinreact has instruction sheets for several automatic analyzers.
Instructions for many of them are available on request.
CALCULATIONS
Calculate the absorbance difference (A2-A1) of each point of the calibration
curve and plot the values obtained against the prealbumin concentration of
each calibrator dilution. Pre-albumin concentration in the sample is
calculated by interpolation of its (A2-A1) in the calibration curve.
QUALITY CONTROL
Control sera are recommended to monitor the performance of manual and
automated assay procedures. It should be used the SPINREACT PROT
CONTROL (Ref.:1102004). Each laboratory should establish its own
Quality Control scheme and corrective actions if controls do not meet the
acceptable tolerances.
REFERENCE VALUES2
Between 20 - 40 mg/dL. Each laboratory should establish its own reference
range.
PERFORMANCE CHARACTERISTICS
Measurement range: Up to 100 mg/dL, under the described assay
conditions. Samples with higher concentrations, should be diluted 1/5 in
NaCl 9 g/L and retested again. The linearity limit depends on the sample
/reagent ratio. It will be higher by decreasing the sample volume, although
the sensitivity of the test will be proportionally decreased.
Detection Limit: Values less than 0,69 mg/dL give non-reproducible
results.
Sensitivity: 4,8 mA / mg/dL (50 mg/dL).
Prozone effect: No prozone effect was detected up to 230 mg/dL.INTERFERENCES
Hemoglobin (16 g/L), bilirubin (40 mg/dL), rheumatoid factors (200 IU/mL),
do not interfere. Lipemia (≥ 8 g/L), interfere. Other substances may
interfere 5,6.
NOTES
1.Clinical diagnosis should not be made on findings of a single test result,
but should integrate both clinical and laboratory data.
