Introduction
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Serum Albumin Test is a commonly performed laboratory test used to measure the concentration of albumin in blood serum.
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Albumin is the most abundant protein present in human plasma and plays an important role in maintaining normal physiological functions.
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It helps in maintaining osmotic pressure and fluid balance between blood vessels and body tissues.
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Albumin also acts as a transport protein, carrying hormones, fatty acids, drugs, vitamins, and other substances in the bloodstream.
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The Serum Albumin Test is widely used in clinical laboratories for evaluating liver function, since albumin is synthesized in the liver.
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It is also helpful in the diagnosis and monitoring of kidney diseases, especially conditions causing protein loss in urine.
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Measurement of albumin levels can indicate nutritional status and protein deficiency in patients.
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Quantitative estimation of serum albumin is commonly performed using automated biochemical analyzers or photometric methods in clinical biochemistry laboratories.
Principle
The most commonly used method for albumin estimation is the Bromocresol Green (BCG) dye-binding method.
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Albumin binds with Bromocresol Green dye at acidic pH (around 4.2).
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This reaction forms a blue-green colored complex.
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The intensity of the color produced is proportional to the concentration of albumin in the sample.
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The absorbance is measured photometrically between 540–630 nm.
Reagents
Reagent 1
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Bromocresol Green
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Succinate buffer
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Sodium azide
Reagent 2
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Albumin standard solution used for calibration.
These reagents are usually supplied in ready-to-use liquid form in diagnostic kits.
Specimen Collection
Sample Type
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Serum
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Plasma (EDTA or heparinized plasma)
Precautions
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Avoid hemolysed samples
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Follow proper sample collection techniques
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Discard contaminated samples
Sample Stability
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Stable for 1 month at 2–8°C
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Stable for 1 week at room temperature
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Stable for up to 3 months at –20°C
Procedure
| Component | Reagent Blank | Standard | Sample |
|---|---|---|---|
| Reagent | 1.0 ml | 1.0 ml | 1.0 ml |
| Standard | – | 0.01 ml | – |
| Sample | – | – | 0.01 ml |
| Distilled Water | 0.01 ml | – | – |
After mixing and incubation, the absorbance of the sample and standard is measured against the reagent blank.
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Wavelength: 578 nm
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Incubation temperature: 37°C
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Incubation time: 1–5 minutes
Calculation
Albumin concentration is calculated using the formula:
Albumin (g/dl) = (Absorbance of Sample / Absorbance of Standard) × Concentration of Standard
Normal Reference Values
| Age Group | Albumin Level |
|---|---|
| Newborn | 2.8 – 4.4 g/dl |
| Children | 3.8 – 5.4 g/dl |
| Adolescents | 3.2 – 4.5 g/dl |
| Adults | 3.5 – 5.2 g/dl |
| Elderly | 3.2 – 4.6 g/dl |
These values may vary slightly depending on laboratory methods and population.
Clinical Significance
- The Serum Albumin Test is clinically important for evaluating various physiological and pathological conditions in the body.
- Changes in serum albumin levels may indicate underlying disorders related to liver function, kidney function, nutritional status, and systemic diseases.
Increased Albumin Levels
Elevated serum albumin levels are relatively uncommon and usually occur due to reduced plasma water content, leading to concentration of albumin in the blood.
High albumin levels may be observed in the following conditions:
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Dehydration – Loss of body fluids due to vomiting, diarrhea, excessive sweating, or inadequate fluid intake may increase albumin concentration in blood.
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Hemoconcentration during venipuncture – Prolonged application of a tourniquet during blood collection can cause fluid to move out of blood vessels into surrounding tissues, resulting in a temporary increase in albumin concentration.
Decreased Albumin Levels
Reduced serum albumin levels, also known as hypoalbuminemia, are more commonly observed and may indicate several pathological conditions.
Low albumin levels may occur in the following situations:
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Liver Diseases – Since albumin is synthesized in the liver, conditions such as cirrhosis, hepatitis, and liver failure can reduce albumin production.
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Kidney Diseases with Protein Loss – In conditions like nephrotic syndrome or chronic kidney disease, albumin is lost through urine, leading to decreased serum albumin levels.
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Malnutrition – Insufficient intake of dietary proteins can reduce albumin synthesis in the body.
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Malabsorption Syndromes – Diseases affecting intestinal absorption, such as celiac disease or chronic intestinal disorders, may decrease the availability of amino acids required for albumin synthesis.
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Protein-Losing Enteropathy – Excessive loss of proteins from the gastrointestinal tract can lead to reduced albumin levels.
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Severe Burns or Skin Diseases – Extensive skin damage may cause loss of proteins from the body, resulting in decreased albumin concentration.
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Chronic Infections or Fever – Increased metabolic activity and protein breakdown during infections can reduce albumin levels.
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Uncontrolled Diabetes Mellitus – Long-term uncontrolled diabetes may increase protein catabolism, contributing to decreased albumin levels.
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Hypertension – Chronic hypertension may affect kidney function and contribute to albumin loss.
