Serum
Definition
The fluid that remains after blood has clotted and the clot has been removed. It is plasma minus fibrinogen and other clotting factors. Serum contains antibodies and other proteins relevant to species testing and historically to blood-group grouping by antibody reaction.
- Composition
- Plasma minus fibrinogen and clotting factors
- Obtained from
- Blood after clotting, clot removed
- Contains
- Antibodies and other proteins
- Forensic relevance
- Species testing, historical blood-group grouping
Common questions
How is serum different from plasma in practice?+
Plasma is collected by centrifuging anticoagulated blood so clotting never occurs, retaining fibrinogen. Serum is collected after the blood is allowed to clot naturally and the clot is removed, so it lacks fibrinogen and other consumed clotting proteins.
Why does serum matter for antibody-based blood grouping?+
Older grouping methods relied on antibody-antigen reactions, and serum is the antibody-carrying fraction of blood, making it the relevant component for those reaction-based typing techniques rather than whole blood or plasma.
Related terms
- Haematocrit
- The proportion of blood volume occupied by red blood cells, approximately 45% in adult males and 40% in adult females. Influences the...
- Haemoglobin
- The iron-containing oxygen-transport protein in red blood cells, composed of four polypeptide subunits each with a haem prosthetic group. Its pseudoperoxidase activity...
- Haemolysis
- The rupture of red blood cells and release of haemoglobin into the surrounding fluid. In casework, haemolysis of aged stains, wet stains,...
- Methaemoglobin
- An oxidised form of haemoglobin in which ferrous iron (Fe2+) is converted to ferric iron (Fe3+), unable to carry oxygen. Its formation...
- Plasma
- The liquid fraction of blood (approximately 55% by volume), containing water, proteins (albumin, immunoglobulins, fibrinogen, clotting factors), electrolytes, glucose, hormones, and dissolved...