Serum:

Serum is the clear, yellowish fluid that remains after blood has clotted and the clot has been removed. It is essentially plasma without the clotting factors (like fibrinogen). Serum can be separated from clotted blood and is used for various blood chemistry tests, but not typically for most hematology tests, which require whole blood or plasma.Reference:Nationally Registered Certified Medical Assistant study materials, clinical laboratory textbooks.