ESR Procedure

Setting Up And Reading An Erythrocyte Sedimentation Rate (ESR): Westergren Method

Principle

The erythrocyte sedimentation rate (ESR) is a non-specific indicator of inflammation in the body and is increased in patients with acute and chronic infections, tissue necrosis or infarctions. The ESR measures the rate at which red blood cells (RBC’s) will settle out of diluted human plasma over a specific period.

In this procedure, a specific volume of whole blood (1 mL) from an EDTA-anticoagulated tube is added to a reservoir containing a diluting fluid. The blood is then brought up to the “zero” mark at the top of a vertical column and sits for 60 minutes to allow the RBC’s to settle towards the bottom of the column. The test is read by measuring the distance from the bottom of the surface meniscus to the top of the red blood cell sediment and reported in millimeters per hour (mm/h).

Materials

• ESR tubes and reservoirs
• ESR rack
• Sharpie
• Timer
• Transfer Pasteur pipettes
• Kim wipes/towels

Sample Type

Freshly collected in EDTA (Lavender topped collection tube) via venipuncture.

Safety Considerations

• All specimens received in the lab must be regarded as potentially infectious so follow safe practices.
• Refer to regulations and safety precautions in the student lab manual located in each student lab.

Procedure

1. Mix the sample for 2 minutes. Any refrigerated samples must be allowed to sit at room temperature for 15-20 minutes before using.
2. Using a sharpie, label the ESR reservoir with patient information (last name, first name, MRN and accession number). MRN and Accession Number are the 2 unique identifiers.
3. Make sure the diluent (saline) in the reservoir is at the bottom of the vial, by shaking or flicking your wrist.
4. Keep the reservoir in an upright position and remove the cap.
5. Using a transfer pipette, add well mixed EDTA-anticoagulated blood to the reservoir, and bring it up to the fill line at the top.
6. Replace the cap securely on both the reservoir and blood tube before continuing.
7. Mix the blood with the diluent by inverting the reservoir about 6-8 times. Make sure the blood is not trapped up inside the cap. Tap the reservoir gently on the bench to remove any trapped RBC’s.
8. Document the rack number and position on the ESR worksheet.
9. Place the ESR tube under the plexiglass face shield and gently penetrate the cap membrane of the reservoir.
10. Slowly insert the ERS tube into the reservoir and watch the blood rise to the zero (“0”) mark at the top.
11. Make sure that the tube is free of air bubbles and properly filled.
12. Place the ESR tube in the proper rack and position.
13. Set a timer for 1 hour and document the time of set up on the ESR worksheet.
14. After 1 hour, record the distance in millimeters from the top of the column of red cells to the bottom of the meniscus of the plasma and document the results on the worksheet. DO NOT include the buffy coat in the measurement.

Procedural Notes

1. Always check to ensure there is diluent in the reservoir.
2. Use a gauze when removing the reservoir cap to avoid any blood splashes.
3. If a face shield is not available, cover the top of the ESR tube with gauze before penetrating the membrane.
4. When plunging the ESR tube into the reservoir use both hands to control the blood flow up the tube.
5. Always double check the ESR tube to ensure it is setup properly and free of debris and air bubbles before setting the timer.
6. Do not include the buffy coat in the reading of the ESR.

Quality

Ideally, the ESR should be set up within 3 hours of collection to avoid falsely low results that may occur if allowed to sit beyond that time.

Normal patient values

• Males: 0-15 mm/h
• Females: 0-20 mm/h

Interpretation

Elevated ESR levels are typically seen in patients with Rheumatoid arthritis, Temporal arteritis, chronic infections, some anemia’s and during pregnancy, to list a few.

Patients with conditions that form rouleaux will have elevated ESR levels. Example, Multiple myeloma.

Abnormal red blood cell morphology associated with some diseases may be associated with decreased ESR levels, including iron deficiency anemia, sickle cell anemia and the presence of spherocytes.^[1]

Sources of Error

1. Elevated fibrinogen levels (hyperfibrinogenemia), excess immunoglobulins (hypergammaglobulinemia) and rouleaux formation will cause an increase in the ESR values.
2. Vibration or tilted ESR tube and refrigerated sample is not brought up to room temperature may cause falsely increased ESR values.
3. A short EDTA draw may result in the sphering/shrinking of the red blood cells leading to falsely low ESR results.
4. Delay in testing, air bubbles or blood clots in the ESR column can cause the ESR to be falsely decreased.
5. Abnormal red blood cell morphology seen in some hematological diseases such as microcytes, sickle cells and spherocytes may also lead to a decreased ESR value.