Background/Purpose: The Westergren Sedimentation Rate (WSR) is a simple, cost-effective laboratory test commonly used by rheumatologists to assess systemic inflammation. This study was initiated to evaluate the current status and availability of the erythrocyte sedimentation rate (ESR) for practicing physicians. Specifically, we aim to compare the accuracy and concordance of the manually performed STAT WSR, processed within two hours of sample collection, with the ESR performed at the central laboratory (CRL), which uses automated capillary photometry. We are particularly interested in whether delays in specimen transport to the CRL impact the reliability of ESR results compared to the more immediate manual WSR.

Methods: We reviewed WSR reports for 106 de-identified patients (Table 1) tested in the POL, and for whom a specimen was also sent the same day to a CRL for erythrocyte sedimentation rate (ESR) testing. This dual testing was initiated after observing that ESR results from the CRL were frequently lower than the POL WSR. Notably, no charges for the in-office WSR.The POL used manual WSR testing. In contrast, the CRL utilized the iSED® system by Alcor, an automated method that directly measures red blood cell aggregation using capillary photometry during rouleaux formation. We also investigated whether the time interval between specimen collection and analysis at the CRL had an impact on ESR comparability.

Results: The ESR measured in the POL was significantly higher than that in the CRL, as demonstrated by both statistical analysis and Passing-Bablok regression (Table 2 and Figure 1). Additionally, we assessed the coefficient of variation (CV) for manual sedimentation rates using three tube comparisons.

Conclusion: This study was conducted to assess the rationale behind requiring WSR specimens to be sent to a CRL and to evaluate how effectively the CRL performs ESR testing. Although the CRL claims its methodology is equivalent to WSR, its ESR testing process is not performed while the specimen is fresh.A WSR must be performed rapidly—ideally within 2 hours of specimen collection—while the blood is still fresh. In the POL it is ordered as a STAT test. Many American patients are covered under insurance plans that either require testing through a CRL or permit POL testing. However, POL testing requires full CLIA certification, which entails substantial administrative overhead, including paperwork, inspections, and associated costs. In-office WSR, by contrast, is a CLIA-waived test, making it a practical option.The CRL uses automated photocytometry for large-scale ESR testing. However, it remains uncertain whether this automated method provides equivalent clinical value when compared to manual WSR. The core concern is the total turnaround time, from the moment the blood is drawn to when the ESR is actually performed. Some CRLs are located far from the physician’s office, in some cases even out of state, necessitating courier or air transport. Often, specimens drawn throughout the day are not shipped until evening. Both resulted in processing delays up to 24 hours or more. This delay could significantly affect clinical decision-making, especially when monitoring conditions such as rheumatoid arthritis using metrics like the DAS28ESR.

Table 1. Patients

Table 2. Statistics

Figure 1. Passing Bablok of the Westergren Sedimentation Rate Compared to the iSED Sedimentation Rate

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