د. زينب

SERUM ALBUMIN

Albumin is the major plasma protein which is unique in being
carbohydrate free. It is a single polypeptide chain containing a solitary
thiol group. It is synthesized in the liver at a rate of 10-12 gm/day. Its
average half life is 21 days.
Functions of albumin:

1- Maintenance of plasma oncotic pressure (colloid osmotic pressure).

2- Transport of lipid soluble anions such as fatty acids, bilirubin,
thyroxine, cortisol, aldosterone, calcium, trace elements and drugs.

3- Source of endogenous amino acids.

Clinical significance
The normal range of serum albumin is 35-52 gm/L (3.5-5.2 g/dl) and
for albumin: globulin ratio is 1.3-1.8.


The factors affecting normal albumin level are the volume of its
distribution, synthetic rate and catabolic rate. In most disease processes a
change in more than one of these factors is operating. Hypoalbuminaemia
is a common indication of illness which may result from:

1- Decreased albumin synthesis; e.g.: liver diseases,

malnutrition and following acute phase response.
2- Increased albumin loss; e.g.: nephrotic syndrome, protein
losing enteropathy and burn.
3- Increased catabolism; e.g.: condition associated with
albumin loss, cushing’s syndrome, thyrotoxicosis, tumors.
Hyperalbuminaemia is not associated with any major clinical
situation. Small elevations are seen in patients with severe dehydration.

Bromocresol Green (BCG) Binding Method

Principle
Albumin and BCG are allowed to bind at PH 4.2 and the absorbance
of the BCG – albumin complex is determined at 625 nm.
At PH 4.2, albumin acts as a cation to bind the anionic dye.

Procedure

1- Into a set of tubes, labeled for standard (std) and test (T) add 4.0 ml
BCG reagent.


2- Add 20 µl. of albumin standard to the (std) tube and 20 µl. of
serum to the (T) tube and mix. Leave for 5 min.

3- Read absorbance of (std) and (T) at 628 nm against BCG reagent

blank.