Biochemistry: Determination of Total Protein in Serum

Total Protein in Serum

• Proteins are organic macromolecular compounds essential for body growth and health.
• Plasma proteins are mainly synthesized by the liver, except for γ-globulins, which are synthesized by plasma cells in lymph nodes, spleen, and bone marrow.

Functions of Plasma Proteins

• Transport: albumin, prealbumin, and globulins
• Maintain plasma osmotic pressure: albumin
• Defense: immunoglobulins and complement
• Clotting and fibrinolysis: thrombin and plasmin

Total Protein Measurement

• Measures the concentration of all proteins in plasma, excluding fibrinogen
• Reflects nutritional status and helps diagnose kidney disease, liver disease, and other conditions

When is it Requested?

• To investigate liver or kidney disorders
• To identify the cause of abnormal fluid pooling in tissue (oedema)
• As part of multiple myeloma investigation

Assay Principle

• Based on the biuret reaction, where divalent copper reacts with peptide bonds of protein under alkaline conditions to form a pink to purple biuret complex

Procedure

• Wavelength: 530-570 nm
• Cuvette: 1 cm light path
• Temperature: 37°C or 15-25°C
• Sample: serum without preparation
• Mix and incubate for 5 min at 37°C or 10 min at room temperature
• Read absorbance (A) against the blank

Calculation

• Total Protein concentration = expected value
• Adult: 6.3-8.3 g/dl
• Child: 6.0-8.0 g/dl

Result Interpretation

Hypoproteinemia

• Causes: prolonged starvation, malnutrition, malabsorption, liver cirrhosis or failure, excessive bleeding, extensive burns
• Symptoms: low total protein levels (< 6.0 g/dl)

Hyperproteinemia

• Causes: increased synthesis due to infections, certain cancers, dehydration, and other conditions
• Symptoms: high total protein levels (> 8.3 g/dl)

Important Notes

• Prolonged application of a tourniquet or standing during blood collection can increase total protein levels
• Certain medications, such as oestrogens, steroids, and oral contraceptives, may affect total protein levels

This quiz covers the concept of total protein in serum, its importance, and determination methods. It's essential for understanding body growth and health, and plasma proteins synthesized by the liver.