Measuring Erythrocyte Sedimentation Rate Using Photometric Rheology Technology Demonstrates Superior Sample Stability as Compared to the Westergren Method

Background/Objectives: Erythrocyte sedimentation rate (ESR) is one of the most widely used tests for assessing inflammatory conditions. Current guidelines require that Erythrocyte Sedimentation Rate (ESR) testing be performed within four hours of collection for samples stored at RT or within 24 h if refrigerated; this is challenging with dispersed collection sites. Thus, we investigated whether testing technology affects sample stability by comparing results obtained using iSED®, based on photometric rheology, with the classical Westergren method. Methods: Samples were evaluated at multiple time intervals. ESR values from each timepoint were plotted against their Time 0 values, and correlation statistics were analyzed using Passing-Bablok regression analysis and a Stability Drift analysis. Samples were considered stable if the correlation statistics of the Passing-Bablok analysis were statistically indistinct from the identity line. Results: Samples in the iSED/RT cohort were stable for up to 28 h after collection, while those in the iSED/4–8 °C cohort were stable for up to 48 h. Samples in the Westergren/RT cohort were stable for up to 10 h after collection, but significantly deteriorated at 12 h and beyond. Conclusions: The iSED methodology provides accurate ESR results for samples stored up to 28 h at RT and 48 h at 4–8 °C, which was significantly superior to the Westergren method for which samples were stable at RT for only 10 h.