Comparative Study between the Westergren and Automated Method for Determination of the Erythrocyte Sedimentation Rate

A comparative study between the standard Westergren and a new automated method for the determination of erythrocyte sedimentation rate (ESR) was performed on 80 individual subjects. From this study, the comparison-of-methods plot automated method (X) and VS Westergren method (Y) gave the least square linear regression equation of Y=0.978 X + 0.64 (r=0.98). Precision analysis gave a coefficient of variation below 3%. At present the new automated method seems to be an effective and safe technique for determination of the erythrocyte sedimentation rate. Chiang Mai Med Bull 2001;40(3):139-141. Suitable and effective techniques for erythrocyte sedimentation rate (ESR) determination are necessary for the success laboratory processes. Several methods to determine the ESR have been developed. Among these, the Westergren method is accepted as a standard technique that has been widely used in Thailand. Although the Westergren method has been popular for its many advantages, the risk to the practitioner regarding contact with blood specimens, which can lead to blood-borne infection, is still high. At present, many new methods to determine the ESR have been developed to decrease the risk. (3) Automated erythrocyte sedimentation determination is an example of newly developed equipment. The automated R tube is a specially designed erythrocyte sedimentation analyzer based on the principle of the electrical impedance of human blood. By using this new technology, the ESR can be easily performed. After application of the collected specimen tube onto the analyzer, determination can be carried out automatically. This new method is currently used in Thailand, but there is no report about its efficacy. Therefore, this study was set as a pilot study to compare this new technique to the Westergren method for determination of ESR. Materials and methods This study was comparative between the classical Westergren and automated method for determination of the ESR. Eighty individual volunteer subjects were included. For each subject, two methods of ESR determination were performed. The first was the Westergren method, which was as standard method, and the second was the automated tube method (Forli Lab, Italy). The automated method was new and made Address requests for reprints: Viroj Wiwanitkit, M.D., Department of Laboratory Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand. E-mail: [email protected] Wiwanitkit V. เชียงใหม เวชสาร 140 use of the electrical impedance principle. The erythrocyte sedimentation rate for each sample was read, and recorded after 1 hour. All recorded data were collected, analyzed and interpreted. Linear regression was performed in order to assess the significant difference in the ESR obtained by the Westergren and automated methods. Results All 80 samples were analyzed for ESR by the Westergren and automated methods. The data from this study are summarized in Table 1. The average difference in value between both methods was 0.240±0.128 mm/hr (p=0.072). The comparison-ofmethods plot automated method (X) VS Westergren method (Y) gave the least square linear regression equation of Y=0.978 X+ 0.64 (r=0.98) (Figure 1). Using the cut off value of 20 mm/hr, the correlation coefficients were 0.958 (p>0.05) and 0.954 Table 1. Characteristics of samples used in the study. Assays Values (mm/hr)