Every blood sample begins to change the moment it leaves the patient’s arm, and most laboratory errors occur before the specimen even reaches an analyzer. This pre‑analytical phase—collection, handling, transport, and storage—accounts for the majority of mistakes, far more than the analytical step that labs spend most of their energy perfecting.
What the ESR Test Measures
The erythrocyte sedimentation rate (ESR) is a routine test clinicians order to gauge inflammation. Unlike a complete blood count, which can sit at room temperature for a day, the ESR has one of the shortest stability windows in hematology. It measures how quickly red blood cells settle through plasma over an hour; higher rates suggest increased protein from inflammatory conditions.
Why Four Hours?
Guidelines from the Clinical and Laboratory Standards Institute and the International Council for Standardization in Haematology state that a Westergren‑based ESR must be run within four hours of collection at room temperature, or within 24 hours if refrigerated. The Westergren method, the historic reference standard, relies on gravity‑based sedimentation and is highly sensitive to temperature and time.
In today’s centralized testing environment, samples often travel from scattered clinics to distant labs in non‑temperature‑controlled trucks. The four‑hour window is therefore frequently exceeded, yet results are still reported, potentially shifting a patient’s classification and treatment plan for conditions such as rheumatoid arthritis, polymyalgia rheumatica, and giant cell arteritis.
New Technology Offers a Longer Window
A study published in August 2026 in Diagnostics compared the classic Westergren column with an automated analyzer called the iSED, which uses photometric rheology. The iSED captures the first seconds of red‑cell aggregation inside a temperature‑controlled flow cell and delivers a result in about 20 seconds. Samples processed with the iSED remained accurate for up to 28 hours at room temperature and 48 hours when refrigerated—far beyond the four‑hour limit of the Westergren method.
Extending the stability window reduces the need for sample rejections, redraws, and second needle sticks, and it allows labs to run the ESR and CBC from a single lavender‑top tube, saving consumables and labor—especially important as lab staffing shortages deepen.
Why Labs Stick With the Old Method
Several factors explain the inertia. First, the Westergren method is the internationally recognized reference standard; regulators, labs, and clinicians trust the familiar benchmark. Second, switching methods requires capital investment, procurement, verification, and staff retraining—costs many labs are reluctant to absorb. Finally, the pre‑analytical phase is often overlooked; labs focus on calibrating instruments while the transport conditions of specimens receive less scrutiny.
When a clinician orders an ESR, they may not know which methodology their lab uses. The newer photometric approach measures a different part of the sedimentation process while shielding the sample from environmental variables, offering a more reliable result without the tight time constraint.
Implications for Patients and Providers
For patients, the newer method means fewer repeat blood draws and less discomfort. For providers, it offers more confidence that the reported ESR reflects the patient’s true physiological state, not an artifact of delayed transport. As labs continue to centralize, adopting technologies that extend sample stability aligns with the goal of delivering accurate, timely care.
While the Westergren method remains the reference, the evidence suggests that laboratories should seriously consider transitioning to automated, photometric ESR analyzers. Doing so would modernize testing, reduce waste, and improve the overall patient experience—an outcome that aligns with the broader mission of delivering high‑quality, efficient health care.
Original reporting: KRDO (Colorado Springs metro) — read the source article.
