Prealbumin (PAB)

Sample

1. This is done on the fresh serum of the patient.
2. 24 hours of the urine sample can also be tested.

Indications

1. It is used to assess nutritional status.
2. As workup in patients with kidney diseases.
3. Advised in subclinical deficit and assessing the response to restorative therapy.

Precautions

1. In the case of inflammation, the result is not representative of the disease.
2. Drugs like anabolic steroids, androgens, and prednisolone increase the level.
3. Drugs like estrogens and oral contraceptives decrease the level.

Pathophysiology

1. Prealbumin is synthesized mainly in the liver.
   1. This was also called transthyretin because of its binding with thyroid hormones.
2. This is the fastest moving protein on the serum electrophoresis.
3. This has the same concentration in the serum and CSF. Due to the low level of other proteins, prealbumin is the major protein in the CSF.
   1. This can be used to differentiate CSF leakage from the nasal secretions.
4. There is a very faint band so normally not seen on the traditional electrophoresis.

5. It binds to T3 and T4 so-called Transthyretin or thyroxine-binding prealbumin.
   1. This is also referred to as thyroxine-binding prealbumin (TBPA).
6. It also binds and carries retinol as a retinol-binding protein which in turn binds Vit.A.
   1. This protein-vitamin complex is essential to transport oil-soluble Vitamin A in the body.
   2. Zinc is required for the synthesis of prealbumin, low levels occur in Zinc deficiency.

7. This is also the amyloid precursor protein and found in cardiac amyloidosis.
8. It has a half-life of 48 hours (1.9 days) which increases its importance superior to Albumin and transferrin.
   1. Albumin’s half-life is 21 days.
   2. Prealbumin is a very good indicator of any change affecting protein synthesis and catabolism.
   3. Because of its short half-life (2 days), prealbumin responds quickly to nutritional intake and nutritional restoration.
   4. It gives the current nutritional status of the body, not the status from 3 weeks ago.
9. It can cross the blood-brain barrier and actively secreted into the cerebrospinal fluid and choroid plexus.
   1. Importance of prealbumin in the nasal secretions to differentiate fluid coming from the skull fracture versus nasal secretion.
10. Prealbumin is also a negative acute-phase protein, serum level decreases in inflammation, malignancy, and protein-losing diseases of kidneys and intestine.
11. Protein status of the patients by estimation of prealbumin:
    1. Mild protein deficiency = 10 to 15  mg/dL
    2. Moderate protein deficiency = 5 to 10  mg/dL
    3. Severe protein deficiency = 0 to 5 mg/dL

Normal level

Source 2

Prealbumin

• Adult = 19 to 38 mg/dl (190 to 380 mg/L)
• Child :
  • <5 days = 6 to 21 mg/dL
  • 1 to 5 years = 14 to 30 mg/dL
  • 6 to 9 years = 15 to 33 mg/dL
  • 10 to 13 years = 22 to 36 mg/dL
  • 14 to 19 years = 22 to 45 mg/dL
• Urine  = 0.017 to 0.047 mg/24 hours
• CSF = around 2% of the total CSF protein

Source 4

Prealbumin

• 19 to 38 mg/dL  (190 to 380 mg/L) by nephlometry

Interpretation

•  In severe protein deficiency =  level is 0 to 5 mg/dl.
• In moderate protein deficiency =  level is 5 to 10 mg/dl.
• In mild protein deficiency = level is 10 to 15 mg/dl.

• (Normal may vary from lab to lab.)

The increased level is seen in :

1. Chronic Alcoholics.
2. Patients with corticosteroid therapy.
3. Hodgkin’s lymphoma.
4. Kidney diseases.
5. Pregnancy.

The decreased level is seen in:

1. In cases of malnutrition.
2. Hypothyroidism
3. Liver diseases.
4. Inflammatory conditions.
5. In cases of trauma like burns.
6. In chronic diseases.
7. In some digestive diseases.
8. In Cancers.
9. Salicylate poisoning.

---