Plasma and serum are both components of blood, but they differ in their composition. The main distinction between the two is that plasma contains clotting factors, while serum does not.
Here are reasons why plasma is preferred over serum in serology tests.
Plasma contains clotting factors, which are essential for blood coagulation (clotting). If the goal of a laboratory test is to evaluate the clotting function of blood, plasma is preferred. Tests such as prothrombin time (PT) and activated partial thromboplastin time (aPTT) are commonly performed on plasma. Read (serum vs plasma )
Plsam is required to measure specific clotting factors (e.g., Factor VIII, Factor IX) for bleeding disorder diagnosis.
Fibrinogen, a clotting factor, is present in plasma but is removed during the clotting process when serum is obtained. If the goal is to measure fibrinogen levels, plasma is necessary.
Plasma is used in blood typing and crossmatching procedures, as these involve assessing the compatibility of blood for transfusions. Plasma contains antibodies that may react with incompatible blood types, making it useful in these scenarios.
Plasma is often preferred over serum for certain virology tests, especially those that involve detecting viruses like HIV, hepatitis, or other bloodborne pathogens. Plasma may contain higher viral loads than serum, providing better sensitivity in some cases.
Plasma is commonly used for therapeutic drug monitoring as it reflects the concentration of drugs in the bloodstream more accurately.
When specific coagulation factor levels need to be measured, such as in the diagnosis of hemophilia or other bleeding disorders, plasma is the preferred sample. This is because clotting factors are present in plasma but are removed during the clotting process when serum is obtained.
Measures of the total protein concentration require plasma instead of serum.