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ESR as Inflammatory Marker
Please check out our Clinical Diagnostics section and Erythrocyte Sedimentation Rate Analyzer / ESR (Sed Rate) Analyzers section for more information or to find manufacturers that sell these products
The erythrocyte sedimentation rate (ESR), or the sed rate, is a simple, nonspecific marker of underlying inflammation. It is often used to screen patients with fevers of undetermined origin, arthritides, muscle pains, and other vague symptoms. ESR testing is specifically indicated for certain conditions: to monitor rheumatoid arthritis, tuberculosis, and systemic lupus erythematosis; and to diagnose and monitor giant cell arteritis and polymyalgia rheumatica. An elevated ESR may also be associated with many other conditions, including other autoimmune disease, anemia, infection, and malignancy.
ESR testing has long been used in the clinical setting. Measurement of the erythrocyte sedimentation rate was first described in 1897 by the Polish physician, Edmund Biernacki. In 1918, the method was refined by the Swedish pathologist Robert Sanno Fåhræus and the internist Alf Vilhelm Albertsson Westergren. Years later, the cornerstone ESR testing method is still referred to as the Westergren method, and it is the recommended ESR testing method of the International Committee for Standardization in Hematology. The reference ranges for the Westergren ESR are based on age and sex.
Westergren Method
For the Westergren method, whole blood is mixed with sodium citrate and then added to a standardized calibrated tube, which is allowed to sit for 60 min. After 60 min, sedimentation is measured by recording the number of millimeters between the top of the sedimented red blood cells and the zero mark at the top of the tube. The modified Westergren method uses EDTA as the anticoagulant instead of sodium citrate. For both procedures, the results are expressed as millimeters per hour (mm/hr).
While the Westergren method is a simple test to perform manually, minor technical problems can cause erroneous test results. Common errors include dilution caused by liquid anticoagulant (sodium citrate solution), mixing errors, and handling errors such as tilted tubes and vibrations occurring during the sedimentation period.
Automated Analysis
Today, there are automated ESR systems that provide faster results and address laboratory safety by minimizing contact with blood samples.
Automated Systems Based on the Westergren Method
- Streck, Inc. (Omaha, NE) offers the CE-marked Streck ESR-Auto Plus®, a 10-position automated benchtop ESR analyzer. This instrument uses infrared light that accurately measures the sedimentation rate of erythrocytes in 1.2-mL ESR-Vacuum Tubes that are supplied separately. The vacuum tubes allow direct-draw collection and can be ordered with a Mylar safety coating which provides impact resistance and will contain glass and blood specimens in the event of breakage. Results are measured in mm/hr (modified Westergren method) and are available in 30 min; therefore, the analyzer can handle 20 samples/hr. The company reports >98% correlation with the manual modified Westergren method. The instrument features random access, a built-in printer, sample ID capability, and a 15-minute prediction mode. The ESR-Auto Plus incorporates a quality control system for monitoring the laboratory's quality control program and data can be downloaded to a laboratory information system. This quality control feature of the ESR-Auto Plus eliminates the need to manually record daily runs. Control samples are stored in individual log files that hold up to 100 samples per level. Statistical reports are generated with the following features: standard deviation, percent coefficient of variation, mean, and highest and lowest result.
- Mechatronics USA LLC (East Providence, RI) offers the StaRRsed Compact, a benchtop automated ESR analyzer. It provides a standard Westergren result and conforms to the recommendations of the International Council for Standardization in Haematology. It has a built-in barcode reader and provides full walk-away operation for 30 samples (1.6 mL). The instrument uses existing blood-cell counter racks, and results are available in 30 or 60 min, with continuous throughput. Each machine is equipped with 84 high-precision-bore glass Westergren pipets that can be reused, and each analysis is temperature corrected to 18.3 ºC. There is a citrate diluter system, so that a sample can be taken from an EDTA blood collection tube, which is manually loaded. Hazy samples can be detected by an optical reader.
Automated System Using an Alternative Method
- HemaTechnologies (Lebanon, NJ) offers the ESR STAT™ PLUS analyzer, a second-generation automated sed rate analyzer that uses EZ-SAFE™ Mylar-wrapped, self-sealing analysis tubes. The ESR STAT PLUS provides sed rates in 5 min from three 25-μL samples. The blood is taken from EDTA blood collection tubes. It has a direct-read feature, but can be used with a barcode reader/printer. The company reports 0.96% correlation with the Westergren method. The ESR STAT PLUS employs centrifugation at 1500 to 2000 rpm for 3 min, and an infrared laser tracks the erythrocyte–plasma interface and makes multiple measurements, from which the linear portion of the sedimentation curve is identified and used by the software algorithm to determine the ESR result (mm/hr).
Choosing an Automated ESR System
Automated erythrocyte sedimentation rate analyzers improve workflow, turnaround time, and laboratory safety. Automated ESR analyzers also allow for uncomplicated sed rate determination and quality control. Depending on your laboratory's requirements, key considerations include capacity, analysis time, throughput, and dimensions.
Please check out our Erythrocyte Sedimentation Rate Analyzer / ESR (Sed Rate) Analyzers section for more information or to find manufacturers that sell these products