Erythrocyte sedimentation rate (ESR) is a common inexpensive and non-specific hematology test frequently ordered in clinical medicine. Still, it remains the most widely used laboratory test for monitoring the course of infections, inflammation, some types of cancer. In addition, it serves as a general sickness index when it is used in conjunction with the patient’s clinical history and physical examination (1–3).
Increased amount of the plasma proteins like fibrinogen are the major factors increasing the ESR test results by reducing the negative electrostatic force between red blood cells (RBCs) leading to an increased rate of rouleaux formation and the RBCs easily falling down within the plasma (4, 5). In case of inflammatory and infectious processes, the fibrinogen concentration in the blood increases the rouleaux formation and the RBCs settle faster than normal (6, 7).
The ESR test is commonly increased in some chronic infectious conditions like active tuberculosis, infective endocarditic, systemic infection, bone infections, rheumatic fever and severe skin infections. It is also important for the assessment of severity of inflammatory bowel disease in children (8–11). It also has been used as a marker of response to treatment in tuberculosis. Moreover, increased ESR can be an early predictive marker of HIV seropositive progression towards AIDS. Additionally, increased ESR can be used as an inexpensive “sickness index” in the elderly (12).
In general, the result of ESR is raised in a wide range of infectious, inflammatory, generative, malignant conditions and associated factors including anemia, pregnancy, hemoglobinopathies, hemoconcentration, and the treatment of anti-inflammatory drugs which changes the plasma proteins that increases in fibrinogen, immunoglobulin, and C-reactive protein (13 –14).
The principle of the ESR determination is based on the measurements of the sedimentations rate of aggregated erythrocytes in plasma. The International Council for Standardization in Hematology (ICSH) recommended the Westergren method as the method of choice for ESR determination. When anticoagulated blood is placed in Westergren tube in vertical column, the erythrocytes normally settle quite slowly by the influence of gravity and the distance of erythrocytes falling down in a vertical column from the plasma in within one hour (15–17).
Undiluted specimens anticoagulated with EDTA reduce the risk of pre-analytic mistakes due to a partially coagulated specimen or to small clots, an altered blood/sodium citrate (SC) ratio, and problems linked to the final volume, inherent mainly in techniques using special tubes for both specimen collection and ESR measurement (18, 19). Using undiluted blood with K3EDTA is a recommended specimen for ESR determination by ICSH because it gives a more reliable result than the traditional SC (20, 21). However, according to the 2011 ICSH recommendations, the reference method for the measurement of the ESR should be based on the Westergren method with modifications that use either whole blood anticoagulated with EDTA and later diluted with SC or saline (4:1) or whole blood anticoagulated with SC (4:1) in Westergren pipettes (22).
Even though various researches were conducted in relation to ESR value among different disease, no studies have conducted on comparison of ESR value between blood mixed with SC and EDTA in the study area. Even though ESR test is one of the commonest investigations carried out in the clinical hematology laboratory, there is no recognized standard control sample available for monitoring the test. The reliability and reproducibility of the results depends on the use of correct methodology. So, this study was aimed to assess the variability of the two commonly used anticoagulants.