Serum albumin is a protein synthesized by the liver and present in the bloodstream. It is essential for maintaining the osmotic pressure that keeps fluids within blood vessels, thereby preventing edema in surrounding tissues. Additionally, serum albumin functions as a transport protein, binding and carrying various substances, including hormones, vitamins, drugs, and ions, throughout the body. Due to its high concentration and small molecular size, it is a crucial biomarker for evaluating liver and kidney function, nutritional status, and various pathological conditions.
Why is this test performed?
This test is performed to evaluate various conditions and diseases, including nephrotic syndrome, liver diseases, kidney diseases, malnutrition, and severe burns.
Sample Collection
To estimate serum albumin levels, a patient's serum is required. While a random blood sample may be used, a fasting sample is preferred for more accurate results.
Approximately 3 to 5 ml of blood is collected in a plain test tube. The blood is allowed to clot, and then centrifuged for 5 to 10 minutes to separate the serum. The serum can be stored at 4°C and remains stable for up to 72 hours.
Precautions
- A fasting blood sample is preferred for more accurate results.
- Avoid specimens with lipemia or hemolysis as they can interfere with the test accuracy.
Pathophysiology
- Albumin is the most abundant protein in the blood.
- Plasma proteins are categorized into three major groups:
- Albumin
- Globulins
- Fibrinogen
- Electrophoresis is the most common method used to analyze plasma proteins, separating them into five bands:
- Albumin
- α1 fraction
- α2 fraction
- β fraction
- γ fraction
- Albumin constitutes 40 to 60% of total plasma protein. Key points about albumin include:
- Due to its low molecular size and high concentration, it is present in urine, cerebrospinal fluid (CSF), interstitial fluid, amniotic fluid, and most extravascular fluids.
- Albumin is highly water-soluble due to its negative charge at normal pH.
- The half-life of albumin is approximately 15 to 19 days.
- It is highly sensitive to liver damage.
- Albumin helps maintain osmotic pressure within blood vessels, preventing fluid leakage.
- It is synthesized in the liver, reflecting both liver and kidney functions.
- Albumin binds to calcium, bilirubin, free fatty acids, and various drugs.
- Low albumin levels can cause edema.
- Decreased albumin synthesis is observed in acute or chronic liver diseases, malignancy, amyloidosis, and malnutrition.
- Albumin plays a crucial role in transporting calcium, bilirubin, bile acids, metal ions, and drugs, with its concentration varying accordingly.
- The presence of albumin in urine indicates kidney disease.
- Dehydration leads to increased albumin levels (hyperalbuminemia).
- Albumin acts as a carrier protein for calcium, bilirubin, progesterone, and various drugs.
- It provides nutrition to tissues and binds to various molecules like vitamins, hormones, and drugs.
Terminology
Hypoalbuminemia
This condition is characterized by albumin levels in the blood/serum that are lower than normal values.
Hyperalbuminemia
This condition is characterized by albumin levels in the blood/serum that are higher than normal values.
Normal Values
- Normal range 3.4 to 5.5 g/dL (35 to 55 g/L)
- Male 4.2 to 5.5 g/dL
- Female 3.7 to 5.3 g/dL
- Cerebrospinal Fluid 15 to 45 mg/dL
- Urine (Spot Urine) 1 to 14 mg/mL
- 24-hour Urine 15 to 45 mg/24 hours
- Newborn 2.8 to 4.8 g/dL