Test Overview
Brookfield Cone/Plate Viscometer
Detection of hyperviscosity states in myeloma, macroglobulinemia, polycythemia and other abnormalities of formed blood elements.
Plasma Viscosity: 1.35 - 1.85 cP. Whole blood viscosity report includes a concurrently measured patient hematocrit and the derived whole blood viscosity expressed as "equivalent hematocrit".
* Reference ranges may change over time. Please refer to the original patient report when evaluating results.
Blood viscosity varies directly according to the composition of blood, i.e., hematocrit and protein.
Test Details
8 hours
- Whole Blood Viscosity, Plasma Viscosity
Specimen Requirements
Collect blood in a 7 mL green top tube. Refrigerate and send intact specimen. Specimen may be stored refrigerated for up to 4 days.
Additional Information
Test includes directly measured plasma viscosity and the derived whole blood viscosity. Most patients do not become symptomatic until the plasma viscosity exceeds 4.0 cP. Usually, a given patient's symptoms will reproducibly appear at a given viscosity, although this will vary from patient to patient.
Whole Blood and Plasma Viscosity: Interpretation
Anticoagulated whole blood and plasma viscosity are measured using a Brookfield cone-plate (rotary) viscometer. Samples are warmed to 37 degrees in order to recapitulate core body temperature. The torque necessary to overcome the viscous resistance of whole blood or plasma is measured in centipoise (cP).
Whole blood viscosity measurements are converted from centipoise to "equivalent hematocrit". (The conversion from cP to hematocrit equivalent is based on the mathematical relationship between these two units of measure).
Whole blood viscosity- expressed in equivalent hematocrit can be thought of as "this whole blood is as viscous as the whole blood would be if its hematocrit were X"
Example 1: Patient A's reported whole blood viscosity is 54%; his concurrent (actual) hematocrit is 36%. In this example, the whole blood is more viscous than would be expected- based on hematocrit - therefore element(s) in addition to RBC, contribute to the increased whole blood viscosity. This is most likely will be protein- e.g. an M-protein. If an M-protein is responsible, the plasma viscosity, expressed in cP, will also be increased above the upper limit of normal. (It will also be informative to directly perform an assay (Monoclonal gammopathy evaluation) to identify the M-protein.)
Example 2: Patient B's reported whole blood viscosity is 58%; her concurrent (actual) hematocrit is 58%. In this example, the whole blood is as viscous as would be expected- based on hematocrit- therefore the observed hyperviscosity is attributable to the increase in RBCs (polycythemia).
Questions? Please contact the Immunology Laboratory Director (J. Warren, M.D.; warren@med.umich.edu; 734-548-4793) or the Pathologist on call for Immunology (734-936-4000).