Erythrocyte sedimentation rate (ESR) is a common inexpensive, sensitive and non-specific hematology test frequently ordered in clinical medicine. It is the most widely used laboratory test for evaluating and monitoring the courses of infections, acute phase inflammation, autoimmune and malignant diseases. In addition, it serves as a general sickness index when it is used in conjunction with patient’s clinical history and physical examinations (1-6).
Increased amounts of the plasma proteins, like fibrinogen are the major factors which increase ESR test results by reducing the negative electrostatic force among red blood cells (RBCs), leading to an increased rate of rouleaux formation and the easy falling down of RBCs within plasma (7, 8). In cases of inflammatory and infectious processes, fibrinogen concentration in the blood increases rouleaux formation and RBCs settle faster than normal (9, 10).
An elevated ESR is often observed in cases of infectious diseases (Tuberculosis (TB), bone and severe skin infections), malignancy, inflammatory or destructive processes, auto immune diseases and rheumatic fever (11-13). As well as in collagen vascular and infective endocarditic diseases (12, 13). It is also important for the assessment of the severity of inflammatory bowel diseases in children (14-17) and marking responses to the treatment of TB (18, 19). Moreover, an increased ESR can be an early predictive marker of HIV seropositive progression towards AIDS (20, 21). Besides, increased ESR can also be used as an inexpensive “sickness index” in the elderly (22).
A raised result of ESR is observed in a wide range of infectious, inflammatory, generative and malignant conditions and associated occurrences, like anemia, pregnancy, hemoglobinopathies, hemoconcentration and the treatment of anti-inflammatory drugs which change plasma proteins that increase in fibrinogen, immunoglobulin, and C-reactive protein (23, 24).
The principle of the ESR determination is based on the measurements of sedimentation rates of aggregated erythrocytes in plasma. The International Council for Standardization in Hematology (ICSH) recommended the Westergren method as a choice for ESR determination. When anticoagulated blood is placed in a Westergren tube in vertical column, the erythrocytes normally settle quite slowly by the influence of gravity, and the distance of erythrocytes falls down in a vertical column from the plasma in within one hour will be taken as ESR value (25-27).
For ESR determination, blood anticoagulated with 3.8% trisodium citrate (TSC) or ethylene diamine tetra acetic acid (EDTA) can used. Using undiluted blood anticoagulated with K3EDTA is a recommended specimen for ESR determination by ICSH because it gives a more reliable result than the traditional TSC (21, 28) by reducing the risk of pre-analytic mistakes due to a partially coagulated specimen or small clots, an altered blood/trisodium citrate (TSC) ratio, and problems linked to the final volume, inherent mainly in techniques using special tubes for both specimen collection and ESR measurement (25, 26). 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 TSC or saline or whole blood anticoagulated with TSC in a 4:1datution ratio in Westergren pipettes (29).
Despite the fact that the ESR test is one of the commonest investigations carried out in the clinical hematology laboratories, there has been no recognized standard control sample for monitoring the test. The reliability and reproducibility of the results depends on the use of correct methodologies. Although, a variety of research was conducted on a matters relating to ESR values of different diseases, no attempts were made to compare the ESR values of blood mixed with TSC and EDTA in the study area. So, this study aimed to assess the variability of ESR values of the two commonly used anticoagulants in individuals suffering from presumptive TB.