Length of erythrocyte sedimentation rate (ESR) adjusted for the hematocrit: reference values for the TEST 1 method

It is known that the erythrocyte sedimentation rate is related to the erythrocyte concentration in blood. Recently, some authors have proposed a method for estimating the relation between the Westergren erythrocyte sedimentation rate and the erythrocyte sedimentation rate adjusted on an hematocrit of 0.35 L/L. In this study we firstly evaluated in 236 samples the relation between the erythrocyte sedimentation rate measured by the TEST 1 analyzer in samples corrected to 0.35 L/L of hematocrit and the erythrocyte sedimentation rate measured in undiluted samples, and the hematocrit and the hemoglobin concentration, obtaining a multiple correlation coefficient of 0.956; (p < 0.001). Comparison between the corrected for HCT erythrocyte sedimentation rate, measured vs estimated, showed a bias of 0.0 (0.95 CI: -0.98 to 0.98 mm/h) with an agreement limit +/- 14.5 mm/h. Then, the reference intervals for the estimated erythrocyte sedimentation rate at 0.35 L/L of hematocrit were calculated by means of an indirect method (Kairisto), using the one-year stored data (47810 results) in our laboratory database. Our data showed that the erythrocyte sedimentation rate corrected to 0.35 L/L of hematocrit could be estimated by a simple formula using the TEST 1 results; the reference ranges were higher than the reference ranges for uncorrected samples. New reference intervals were needed for an improved evaluation of the patients, and a table of reference intervals for age and sex is presented.