Problem 8 - Clinical Chemistry

Question

Which of the following would indicate a plasma specimen was used for protein electrophoresis instead of serum? a. A small peak between the \(\beta\) - and \(y\) -globulins b. A broad increase in the \(\gamma\) -globulin fraction c. A bridge between the \(\alpha_{1}\) - and \(\alpha_{2}\) -globulins d. A significantly decreased albumin peak

Step-by-Step Solution

Answer

a. A small peak between the \beta\beta\- and \gamma\-globulins

Step 1: Understand the difference between plasma and serum

Plasma is the liquid component of blood that has not clotted and still contains clotting factors. Serum is the liquid part of blood once it has clotted and does not contain clotting factors.

Step 2: Know the components involved in protein electrophoresis

Protein electrophoresis separates blood proteins into several components: albumin, \(\beta \)-globulins, \(\beta \)-globulins, \(\beta \)-globulins, etc. Plasma contains fibrinogen, a clotting factor, which is not present in serum.

Step 3: Identify the additional peak in the electrophoresis graph

If plasma is used instead of serum, there will be an extra peak present in the electrophoresis pattern. This peak is usually found between the \(\beta\beta\)-globulin and \(\gamma\)-globulin fractions, indicating the presence of fibrinogen.

Step 4: Match the extra peak with the given options

Among the options provided, a. 'A small peak between the \(\beta\beta\)- and \(\gamma\)-globulins' aligns with the appearance of fibrinogen in the electrophoresis if plasma was used instead of serum.

Key Concepts

Plasma vs Serum

Both plasma and serum are important components of blood, but they have distinct differences. Plasma is the liquid part of blood that contains water, salts, enzymes, antibodies, and other proteins. Plasma is present in blood before it clots and retains all clotting factors such as fibrinogen.

Serum, on the other hand, is the liquid that remains after blood has clotted. When blood clots, it uses up the clotting factors, which means serum does not contain fibrinogen. Therefore, serum is essentially plasma minus the clotting factors.

Understanding the difference between plasma and serum is crucial when performing protein electrophoresis, which is a technique used to separate proteins based on their size and charge. This knowledge helps in identifying specific peaks and patterns in the electrophoresis graph that indicate the use of either plasma or serum.

Blood Proteins

Blood proteins play a variety of roles in the body, including maintaining oncotic pressure, immune response, and blood clotting. Key blood proteins include:

• Albumin: This is the most abundant protein in plasma and maintains the osmotic balance between blood and tissues.
• Globulins: These proteins are divided into alpha, beta, and gamma globulins. Gamma globulins include antibodies that are vital for immune function.
• Fibrinogen: This is a crucial clotting factor that is present in plasma but absent in serum.

In protein electrophoresis, these proteins are separated into distinct bands. Each fraction (albumin, alpha-globulins, beta-globulins, and gamma-globulins) can provide valuable diagnostic information. For instance, a broad increase in the gamma-globulin fraction may indicate chronic inflammation or infection. If plasma is used instead of serum, an additional peak (due to fibrinogen) will appear between the beta-globulin and gamma-globulin fractions.

Fibrinogen

Fibrinogen is a vital protein in the blood that's necessary for blood clotting. When an injury occurs, fibrinogen is converted by thrombin into fibrin, which forms a mesh that helps to stop bleeding by trapping blood cells.

Fibrinogen is present in plasma but not in serum. Therefore, its presence is a key indicator in differentiating whether a blood sample is plasma or serum.

In protein electrophoresis, if plasma is used, an extra peak can be observed between the beta-globulin and gamma-globulin fractions, indicating the presence of fibrinogen. This is not seen if serum is used for the electrophoresis. Understanding the role and behavior of fibrinogen helps in accurately interpreting electrophoresis results and avoiding diagnostic errors.