Plasma and serum viscosity tests are useful to detect an acute phase reaction or severe inflammatory response such as occurs in sepsis. Serum viscosity is tested using a rotating or capillary viscometer and is marginally lower than plasma because the clotting factors have been removed.

Then, after coagulation, the specimen is centrifuged to separate the serum from the clotted blood.

Serum is similar to plasma, except that the blood is drawn into a collection tube without anti-coagulant and allowed to clot for about 20 minutes. Plasma viscosity is tested using a rotating or capillary viscometer using the separated plasma only. The plasma contains the dissolved proteins, clotting factors, and other suspended materials in water. Blood is drawn into a collection tube that contains an anti-coagulant (EDTA or citrate) and placed in a centrifuge to separate the cells from the plasma. Plasma is typically about 55% of the blood volume. Plasma differs from whole blood in that the cellular material has been removed by centrifugation. serum or plasma, and in addition, explains the critical importance of obtaining a complete viscosity profile and not just the systolic viscosity measurement.

This white paper describes the difference between viscosity measurements for whole blood vs. Additionally, a very select few number of clinical reference labs claim to provide whole blood viscosity testing, however these tests are for systolic blood viscosity-high shear rate viscosity only. There are many reference laboratories and pathology departments of hospitals that can provide clinical viscosity testing, however these tests are for serum and plasma viscosity, not whole blood. Meridian Valley Laboratory is the only clinical reference lab that provides a comprehensive blood viscosity profile, which includes both systolic and diastolic blood viscosity measurements.

Plasma viscosity test