A-132 Extending Erythrocyte Sedimentation Rate Sample Stability from Four Hours to 28 Hours Using Photometric Rheology

Abstract Background Erythrocyte sedimentation rate (ESR) is one of the most common lab tests in the world. It is a non-specific laboratory test for assessing or monitoring patients with subclinical, acute, or chronic inflammatory conditions. Traditional ESR testing is done via the manual Westergren method, but many laboratories have adopted automated ESR analyzers to minimize hands-on time and increase turnaround time. Even though workflow has improved, sample stability for ESR testing remains limited: 4 hours for room temperature samples and 24 hours for refrigerated samples. These storage limitations for traditional ESR testing are consistent between guidelines and ESR results are known to degrade when samples are stored too long or incorrectly. These stability constraints are unrealistic in reference/centralized laboratory settings when specimen collection locations are widely dispersed and refrigerated sample storage during transport is unavailable or poorly controlled. The iSED ESR analyzer family (miniiSED, iSED, iSED ELITE, and iSED PRO) uses photometric rheology to generate an ESR value by assessing RBC aggregation which significantly increases sample stability to 28 hours for both room temperature and refrigerated samples. Methods In ESR, the degree of RBC aggregation determines the degree of sedimentation. The iSED analyzer family employs a common analytical unit and utilizes photometric rheology technology to measure rouleaux formation (which occurs during the lag phase of RBC sedimentation) instead of sedimentation at 60 minutes. The iSED analyzers have demonstrated equivalence with the Westergren reference method via analyzer-specific method comparison studies using fresh samples. Stability of iSED analyzer family results was examined by performing a correlation analysis of aged sample results vs. fresh sample (within 4 hours of collection) results from samples spanning the analytical range at defined time intervals. Both refrigerated and room temperature cohorts were evaluated. Results Since ESR is a physiological process, Passing-Bablok regression was used to compare aged sample results to fresh sample results. The storage condition and duration was considered acceptable if the 95% CI of slope included 1.0, the 95% CI of intercept included 0.0, and the Spearman correlation coefficient was = 0.90. The cohort of room temperature samples (n=94) at 28-hours compared to fresh samples demonstrated the following acceptable regression statistics: slope = 0.93 with a 95% confidence interval of 0.8627 to 1.0000, intercept = -1.65 with confidence interval of -4.0000 to 0.1471 and a Spearman correlation coefficient of 0.928. Regression statistics of the 28-hour vs baseline comparison for the refrigerated cohort (n=57) were: slope = 0.94 with a 95% confidence interval of 0.9167 to 1.0000, intercept = -0.67 with confidence interval of -2.0000 to 0.08333 and a Spearman correlation coefficient of 0.994. Conclusion The photometric rheology-based technology utilized by the iSED family of analyzers improves ESR sample stability and better aligns with real world sample processing timelines. ESR samples tested with the iSED family of analyzers are stable for up to 28 hours when stored room temperature or refrigerated which significantly improves sample transport logistics and result quality.