Prealbumin (As a Acute phase protein)
- The venous blood of the patient is needed to prepare the serum.
- This can be estimated in the 24 hours of urine and CSF.
- Marker for the patient with nutritional status.
- It is a sensitive indicator of protein synthesis and catabolism.
- If there is co-existent inflammation, then test result interpretation is not possible.
- Drugs increasing the level are anabolic steroids, androgens, estrogens, and prednisolone.
- Drugs that may decrease the level are amiodarone, estrogens, and oral contraceptives.
- In 1995, the joint committee on Accreditation of health organization first issued the main parameter to assess the patient nutritional status, to identify all patients with malnutrition.
- For a long time albumin was the parameter for the nutritional status (malnutrition). Now it is found that prealbumin is the better choice because of the short half-life of 1.9 days.
- Prealbumin is one of the major proteins.
- Prealbumin has a shorter half-life of 2 days (1.9 days).
- Prealbumin half-life of 2 days is much less than the albumin of 21 days.
- Because of its short half-life, prealbumin is a better indicator of synthesis and catabolism.
- This is usually indicated to monitor the effectiveness of parenteral nutrition therapy.
- This is present in the serum and CSF.
- This is the main component of the CSF proteins. It can cross the blood-brain barrier, so it is secreted into the CSF by the choroid plexus.
- Prealbumin is the faster-migrating protein on the serum electrophoresis. Because of the less amount, it is not seen on the traditional serum electrophoresis.
- But this is seen in the CSF protein electrophoresis.
- The purpose of CSF electrophoresis is to diagnose multiple myelosclerosis by finding the oligoclonal band.
- The pre-albumin binds and transport:
- Prealbumin binds retinol-binding protein (RBP), which in turn binds vitamin A.
- It plays role in the transport and metabolism of vitamin A. This protein-vitamin complex formation is necessary to transport the oil-soluble vitamin A through the body.
- Prealbumin sometimes referred to as thyroxine-binding prealbumin (TPA). It does not play a major role in thyroid hormone functions.
- It binds T3 and T4, so it is also called transthyretin and thyroxine-binding prealbumin (TBPA).
- Mainly there is the secretion of the T4 and only about 7% is T3. In the blood >99% of T4 and T3 are bound to serum proteins. About 80% to 85% of T4 is bound to T4-binding globulin (TBG), and α-1 globulin; about 10% to 15% to prealbumin.
- The pre-albumin binds and transport:
- Importance of the prealbumin:
- Prealbumin levels in the serum fluctuate more rapidly in response to the synthesis rate, in comparison to other serum proteins.
- Because of this property, prealbumin is a useful indicator of nutritional status.
- Prealbumin decreases in hepatobiliary diseases because of impaired synthesis.
- The serum level of prealbumin is a better indicator of liver synthetic function than albumin.
- Zinc is needed for the synthesis of prealbumin, so in case of deficiency of zinc, there will be a low level of prealbumin.
- The increased level was seen in Hodgkin disease and chronic kidney diseases.
- This is a good marker than albumin and transferrin.
- This is a better indicator of liver synthetic activity.
- Prealbumin is the precursor of the amyloid in senile cardiac amyloidosis.
- A mutant version of prealbumin (transthyretin) is responsible for familial amyloid polyneuropathy.
The severity of malnutrition:
|The severity of the malnutrition||Prealbumin level|
|Mild||10 to 15 mg/dL (100 to 150 mg/L)|
|Moderate||5 to 10 mg/dL (50 to 100 mg/L)|
|Severe||0 to 5 mg/dL (0 to 50 mg/L)|
- Prealbumin is a negative acute-phase reactant protein.
- Its level decreases in malignancy, and inflammation.
- Also, it is decreased in the protein-losing diseases of the intestine and kidneys.
- Prealbumin because of the small quantity in the blood, may not be detected on serum electrophoresis. As it can cross the blood-brain barrier, so may be found in the CSF electrophoresis.
- The medicolegal and medical importance of prealbumin:
- The absolute concentration of the prealbumin in CSF and serum is the same. because of the low level of other proteins, prealbumin is the major protein in the CSF.
- So prealbumin can be used as a marker when there is leakage of the fluid from the nose or from the fracture of the skull.
- Prealbumin will differentiate nasal secretion from the leakage of CSF from the brain.
Normal values of prealbumin
|Adults/elders||15 to 36 mg/dL (150 to 360 mg/L)|
|<5 years||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 24 hours sample||0.017 to 0.047 mg/day|
|CSF||Approximately 2% of the CSF total proteins|
|Critical value||<10.7 mg/dL (indicate severe malnutrition)|
Another source of prealbumin
- 19 to 38 mg/dL ( 190 to 380 mg/L) by nephelometry.
The decreased level of prealbumin is seen in:
- In hepatocellular dysfunction. There is a diminished synthesis of prealbumin.
- It is decreased in tissue damage.
- In inflammation. As it is a negative acute-phase protein, so its level will decrease in the inflammatory conditions.
- In malnutrition.
- In burn, there is acute loss of protein from the burn area.
- Drugs like oral contraceptives, Estrogen, and amiodarone.
- Salicylates poisoning.
The increased level of prealbumin is seen in:
- In Hodgkin’s disease.
- In chronic kidney diseases.
- Some cases of nephrotic syndrome.
- In pregnancy
- Drugs like steroids, prednisolone, and androgens.
- Chronic alcoholics.
- Critical value = when <10.7 mg/dL
- This indicates severe nutritional deficiencies.