The erythrocyte sedimentation rate (ESR or sed rate) measures the rate at which RBCs in anticoagulated blood settle to the bottom of a calibrated tube. In normal blood, relatively little settling occurs because the gravitational pull on the RBCs is almost balanced by the upward force exerted by the plasma. If plasma is extremely viscous or if cholesterol levels are very high, the upward trend may virtually neutralize the downward pull on the RBCs. In contrast, anything that encourages RBCs to aggregate or stick together increases the rate of settling. Inflammatory and necrotic processes, for example, cause an alteration in blood proteins that results in clumping together of RBCs because of surface attraction. These clumps are called rouleaux. If the proportion of globin to albumin increases or if fibrinogen 3 levels are especially high, rouleaux formation is enhanced and the sed rate increases.³³ Specific causes of altered ESRs are presented in Table 1-10.

• Normal values for the ESR follow. Note that several laboratory methods can be used to determine the ESR. Values vary according to the method used.

Delays in performing the test after the sample is collected may retard the ESR and cause abnormally low results; the test should be performed within 3 hours of collecting the sample.

• Suspected organic disease when symptoms are vague and clinical findings uncertain
• Identification of the presence of an inflammatory or necrotic process
• Monitoring response to treatment for various inflammatory disorders (e.g., rheumatoid arthritis, systemic lupus erythematosus)
• Support for diagnosing disorders associated with altered ESRs (see Table 1-10)

Nursing Care Before the Procedure

Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

A venipuncture is performed and the sample collected in a lavender-topped tube. A capillary sample may be obtained in infants and children as well as in adults for whom venipuncture may not be feasible.

The sample should be transported promptly to the laboratory, because the test must be performed within 3 hours of collecting the sample. Delays may retard the ESR and cause abnormally low results.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample (see Appendix I).

• Abnormal values: Note and report increases or decreases in the rate in relation to other test results used to determine the presence of or to monitor the progress of a disease. As the rate increases, note signs of infection or inflammation (pain, temperature) and activity intolerance (fatigue, weakness), and perform activities that conserve the client's energy. Administer ordered anti-inflammatory or antibiotic therapy. As the rate decreases, evaluate for improvement in condition and possible increases in client activity.