Why is plasma not suitable for protein electrophoresis?

Plasma is not suitable for protein electrophoresis primarily because of the presence of fibrinogen, which can lead to diagnostic inaccuracies. During electrophoresis, fibrinogen can produce a band that may be mistakenly interpreted as a small monoclonal protein or as part of a disease state, such as multiple myeloma. This resemblance can obscure the analysis of true monoclonal proteins because fibrinogen is a large protein that can migrate similarly to smaller proteins, creating a potential for confusion in interpretation of the electrophoretic patterns.

In contrast, serum, which is obtained after blood has clotted, does not contain fibrinogen. As a result, electrophoresis of serum provides a clearer picture of the protein components present, allowing for more accurate identification of abnormalities or pathologies associated with the proteins being evaluated. The presence of fibrinogen in plasma can misrepresent the protein landscape during electrophoresis, which is why serum is preferred for this type of analysis.