Blood plasma viscosity inflammation

by Nathan Wei, MD, FACP, FACR

Nathan Wei is a board-certified rheumatologist and author of the Second Opinion Arthritis Treatment Kit. It's available exclusively at this website... not available in stores.

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Erythrocyte sedimentation rate (ESR) determination is a simple and inexpensive laboratory blood test that is frequently ordered in clinical rheumatology. The test measures the distance that erythrocytes have fallen after one hour in a vertical column of anticoagulated blood under the influence of gravity. The amount of fibrinogen, and therefore viscosity in the blood directly correlates with the ESR. Although there is an enormous amount of literature concerning the ESR, an elevated value remains a nonspecific finding.

Women tend to have higher ESR values, as do the elderly. For unknown reasons, obese people have also been noted to have slightly elevated ESRs. Any condition that elevates fibrinogen (e.g., pregnancy, diabetes mellitus, end-stage renal failure, heart disease, collagen vascular diseases, malignancy) may also elevate the ESR. Anemia and the presence of large red blood cells (macrocytosis) increase the ESR. In anemia, with the hematocrit reduced, the velocity of the upward flow of plasma is altered so that red blood cell aggregates fall faster. Macrocytic red cells with a smaller surface-to-volume ratio also settle more rapidly.

A decreased ESR is associated with a number of blood diseases in which red blood cells have an irregular or smaller shape that causes slower settling.

In patients with polycythemia, too many red blood cells lower the ESR. An extreme elevation of the white blood cell count as observed in chronic lymphocytic leukemia has also been reported to lower the ESR. Hypofibrinogenemia, hypergammaglobulinemia associated with dysproteinemia, and hyperviscosity may each cause a marked decrease in the ESR. Drug therapy with nonsteroidal anti inflammatory agents may decrease the ESR.

Researchers have wondered whether other tests, such as measurement of C-reactive protein, may perform better than the ESR. Repeatedly, the ESR and plasma viscosity determinations have been shown to be the most satisfactory monitors of acute-phase response to disease after the first 24 hours. During the first 24 hours in an inflammatory process, C-reactive protein may be a better indicator of the acute phase response. However, C-reactive protein tests are more expensive, less widely available and more time-consuming to perform than the ESR.

In oncology, a high ESR has been found to correlate with overall poor prognosis for various types of cancer, including Hodgkin's disease, stomach, kidney, breast, colon, and prostate cancer as well as chronic lymphocytic leukemia. In patients with solid tumors, a sedimentation rate greater than 100 mm per hour usually indicates metastatic disease.

Because an elevated ESR may occur in so many different clinical settings, this finding is meaningless as an isolated laboratory value. In addition, some patients who have malignant tumors, infections or other inflammatory disorders will have normal ESR values. Most unexplained ESR elevations are short-lived and not associated with any specific underlying process. In those instances where disease is present, it will usually be obvious after completion of history taking, physical examination and collection of routine laboratory data.

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