Objective: To develop a micro-erythrocyte sedimentation rate (ESR) system with potential to be self-administered by patients at home using capillary blood.
Design: For each subject, three tubes of blood were collected in ethylenediaminetetraacetic acid (EDTA), centrifuged, and the cells separated from the plasma. Plasma was pooled and divided into three aliquots, two of which were spiked with defined amounts of fibrinogen creating a normal ESR and two distinct degrees of ESR acceleration. Fifteen hundred microliters of pooled autologous cells were resuspended in 1500 microL of the three prepared autologous plasmas to standardize hematocrit values. ESRs were performed using the Westergren method and four potential micro-ESR systems, utilizing a micro-hematocrit tube, S/P capillary blood gas tube, Natelson blood collecting tube, and Caraway micro blood collecting tube.
Setting: Saint Louis University, St. Louis MO. PATIENTS/SAMPLES: Twenty-eight volunteers between the ages of 18 and 60 years with no underlying conditions participated in the study.
Interventions: Hematocrit was standardized to approximately 40% for all samples and fibrinogen concentrations of approximately 200 mg/dL, 382 mg/dL, and 563 mg/dL were achieved for each subject.
Main outcome measures: ESRs were measured in mm/hour and in percentage. Micro-ESR values were plotted versus the paired Westergren ESR value and the data were analyzed using Pearson's r correlation.
Results: When compared to the Westergren ESR method, the following correlation coefficients were achieved: S/P tube (r = 0.808), Caraway tube (r = 0.797), Natelson tube (r = 0.719), and micro-hematocrit tube (r = 0.655).
Conclusion: Three of the four micro-ESR methods achieved correlation coefficients acceptable to the authors, with the potential of being converted into a capillary ESR system for in-home use.