Which laboratory technique is widely used to quantify immunoglobulin classes?

• A. Immunonephelometry
• B. Serum protein electrophoresis
• C. Chromatography
• D. Isoelectric focusing

Answer: (A)

Immunonephelometry is the technique most widely used to quantify immunoglobulin classes. It works by reacting the patient’s serum with antibodies specific to a particular immunoglobulin class, forming immune complexes that scatter light. The amount of scattered light is measured and proportional to the concentration of that immunoglobulin in the sample, allowing precise quantification of IgG, IgA, or IgM. This approach is fast, highly specific, and readily automated, which is why it’s a standard method in clinical labs for determining immunoglobulin levels.

Other methods listed serve different roles. Serum protein electrophoresis separates serum proteins into bands to assess the overall protein profile but does not provide precise class-specific quantification. Chromatography can separate proteins but isn’t the routine, rapid method used for measuring immunoglobulin concentrations in most labs. Isoelectric focusing distinguishes proteins by isoelectric point and is more about characterizing immunoglobulin variants than routinely quantifying classes.