Prealbumin (As a Acute phase protein)
Prealbumin
Sample for Prealbumin
- The venous blood of the patient is needed to prepare the serum.
- This can be estimated in the 24 hours of urine and CSF.
Indications for Prealbumin
- Marker for the patient with nutritional status.
- It is a sensitive indicator of protein synthesis and catabolism.
Precautions for Prealbumin
- 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.
Pathophysiology of Prealbumin
- Prealbumin is also called transthyretin.
- In 1995, the joint committee on Accreditation of health organizations first issued the main parameter to assess the patient’s nutritional status to identify all patients with malnutrition.
- For a long time, albumin was the parameter for 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).
- The 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 serum electrophoresis. Because of the less amount, it is not seen in traditional serum electrophoresis.
- But this is seen in the CSF protein electrophoresis.
- CSF electrophoresis aims to diagnose multiple myelosclerosis by finding the oligoclonal band.
Functions of Prealbumin:
- The pre-albumin binds and transports:
- Prealbumin binds retinol-binding protein (RBP), which binds vitamin A.
- It plays a 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 is sometimes referred to as thyroxine-binding prealbumin (TPA). It does not play a major role in thyroid hormone functions.
- It binds T3 and T4, also called transthyretin and thyroxine-binding prealbumin (TBPA).
- Mainly there is the secretion of 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.
Importance of the prealbumin:
- Prealbumin levels in the serum fluctuate more rapidly in response to the synthesis rate than 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 a deficiency of zinc, there will be a low level of prealbumin.
- The increased level was seen in Hodgkin’s disease and chronic kidney diseases.
- This is a good marker than albumin and transferrin.
- This is a better indicator of synthetic liver 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 classification:
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 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 a fracture of the skull.
- Prealbumin will differentiate nasal secretion from the leakage of CSF from the brain.
Normal values of prealbumin
Age | Normal range |
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 (indicates 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 the following:
- 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 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 the following:
- 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.
Questions and answers:
Question 1: What is the value of prealbumin?
Question 2: What is the importance of the prealbumin for the nasal secretion?