Related Experiment Video
Updated: Jun 20, 2026
Erythrocyte Sedimentation Rate: A Physics-Driven Characterization in a Medical Context
Published on: March 24, 2023
Rapid Measurement of Erythrocyte Sedimentation Rate Using a Tube Positioned at a 45° Angle Compared With the
Francis Agyei Amponsah1, Benedicta Serwaa Obeng1, Otchere Addai-Mensah1
1Department of Medical Diagnostics, Faculty of Allied Health Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, knust.edu.gh.
Background:
The erythrocyte sedimentation rate (ESR) is a routine hematological test that can detect and track an increase in the body's inflammatory activity caused by infections, tumors, or autoimmune diseases. Although the test has lower specificity than C-reactive protein in assessing inflammation, it is widely used in resource-limited countries such as Ghana due to its low cost and ease of performance. The conventional Westergren method of ESR estimation takes 1 h, and this could hinder the availability of results in routine clinical workflows. It is in view of this that the present study sought to reduce the turnaround time without compromising on test accuracy by using a method that involved positioning the tube at an angle of 45°.
Methods:
This experimental analytical method comparison study recruited 100 participants (50 pregnant and 50 healthy blood donors) aged between 15 and 40 years. Five milliliters of venous blood was taken from each participant and added to trisodium citrate anticoagulant in a fixed blood-to-anticoagulant ratio of 4:1. For each study participant, two Westergren-Katz tubes were filled with the diluted blood to the 200 mm mark, and one was held vertically at 90° while the other was set at an angle of 45° at room temperature. The ESR value was recorded after 1 h for the vertically (90°) set tube, while the ESR value was read every minute for 10 min for the tube placed at an angle of 45°.
Results:
ESR results obtained from the 6th to the 10th minutes for the tubes placed at an angle of 45° showed comparable results to those recorded at the end of an hour for the tubes set vertically at 90° in both pregnant women and the healthy blood donors (p > 0.05). In both study groups, Bland-Altman plots revealed that ESR measurements taken at the 8th minute at 45° had the best agreement with minimal bias to ESR values at 90° for 1 h.
Conclusion:
This study proved that the turnaround time for the ESR test could be reduced to 8 min if the tube is positioned at an angle of 45°.
