Acute Phase Protein – Part 7 – Albumin and Prealbumin

Acute-phase protein (Acute Phase Reactants)

• Acute-phase protein is raised in inflammatory conditions.
• When there is an increase in a protein called positive acute-phase protein.
  • In the case of a decrease in the acute phase protein, is called negative phase protein.
• The acute phase proteins (positive) are protein whose concentration increases in the plasma and after the disease episode is over then it decreases and may become normal.

Albumin

Sample

• The venous blood of the patient is needed to prepare the serum.
• Try to analyze the fresh sample.
• Can store at 4 °C for <72 hours.
• The serum is stable at -20 °C for 6 months.

Precaution

• Avoid hemolysed and lipemic serum.
• A prolonged tourniquet can raise the level of albumin and other proteins.
• Blood from the side of the I/V drip will dilute the sample.

Indication

1. In renal diseases.
2. In liver diseases.
3. In protein-losing enteropathy.
4. To evaluate nutritional status.
5. It is advised in burns, hemorrhage, leaks in the GI tract, and other chronic diseases.
6. It is advised in the older people.

Pathophysiology

1. Albumin is synthesized in the liver.
   1. It constitutes 60% of the total proteins.
   2. The measurement of albumin gives an idea about the synthetic activity of the liver.
   3. Albumin is the main protein vehicle to transport free fatty acids.
   4. Albumin also transports blood important components like hormones, drugs, and enzymes.

2. The half-life of albumin is 12 to 18 days.
   1. So liver impairment is not detected until the above period.

3. The main function of albumin in the blood is to maintain the colloidal osmotic pressure.
   1. In vascular and extravascular spaces:
      1. Blood.
      2. Urine.
      3. CSF.
      4. Amniotic fluid.
   2. This is a source of nutrition.
   3. This is part of the buffer system.

4. This is the negative acute-phase protein because its amount decreases in the plasma in response to inflammation.
   1. This decrease may be rapid within 24 hours or decreases slowly.
   2. This decrease may be due to the production of cytokines in inflammation.
5. Albumin reduction in concentration is more noticeable in chronic inflammatory conditions.

Normal

• Source 1
• 0 to 4 days            =  2.8 to 4.4 g/dL
  • 4 days to 14 years = 3.8 to 5.4 g/dL
• Adult
  • 18 to 60 years     = 3.4 to 4.8 g/dL
  • 60 to 90 years     =  3.2 to 4.6 g/dL
  • >90 years = 2.9 to 4.5 g/dL
• Source 2
  • Premature infants = 3 to 4.2 g/dL
  • Newborn = 3.5 to 5.4 g/dL
  • Infants = 4.4 to 5.4 g/dL
  • Child = 4.0 to 5.9 g/dL
  • Adult = 3.5 to 5.0 g/dL

The decreased level of albumin is seen in:

1. In malnutrition.
2. After the surgery.
3. In case of a burn.
4. In protein-losing enteropathy.
5. In uropathies.
6. In the third trimester of the pregnancy.
7. In chronic liver diseases.
8. In collagen vascular diseases like lupus erythematosus.
9. Drugs are estrogen and oral contraceptives.

The increased level of albumin is seen in:

1. In Dehydration.
2. Drugs are anabolic steroids, growth hormones, corticosteroids, insulin, and progesterone.

Prealbumin

Sample

• The venous blood of the patient is needed to prepare the serum.
• This can be estimated in the 24 hours of urine and CSF.

Indication

• Marker for the patient with nutritional status.
• It is a sensitive indicator of protein synthesis and catabolism.

Pathophysiology

1. Prealbumin has a shorter half-life of 2 days.
   1. Prealbumin half-life of 2 days is much less than the albumin of 21 days.
2. This is present in the serum and CSF.
   1. This is the main component of the CSF proteins.
3. The pre-albumin binds:
   1. Retinol (RBP) and it also binds the vit.A.
   2. Thyroxin called thyroxine-binding prealbumin (TBA).
4. This is a good marker than albumin and transferrin.
5. This is a better indicator of liver synthetic activity.
6. Prealbumin decreases in acute and chronic inflammation.
   1. Prealbumin is a negative acute-phase reactant protein.
   2. Its level decreases in malignancy, and inflammation.
   3. Also, it decreases in the protein-losing disease of the intestine and kidneys.

Normal

1. Adult = 15 to 36 mg/dL.
2. Child:
   1. <  5 days =6 to 21 mg/dL
   2. 6 to 9 years = 15 to 33 mg/dL.
   3. 10 to 13 years = 22 to 36 mg/dL.
   4. 14 to 19 years = 22 to 45 mg/dL.
3. Urine 24 hours = 0.017 to 0.047 mg/ 24 hours.
4. CSF = 2% of the total CSF proteins.

The decreased level of prealbumin is seen in:

1. In hepatocellular dysfunction.
2. It is decreased in tissue damage.
3. In inflammation.
4. In malnutrition.
5. In burn.
6. Drugs like oral contraceptives, Estrogen, and amiodarone.
   1. Salicylates poisoning.

The increased level of prealbumin is seen in:

1. In Hodgkin’s disease.
2. In chronic kidney diseases.
3. Some cases of nephrotic syndrome.
4. In pregnancy
5. Drugs like steroids, prednisolone, and androgens.

• Critical value = when <10.7 mg/dL
  • This indicates severe nutritional deficiencies.

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