Erythrocyte sedimentation rate: the extinction of a dinosaur laboratory test?
19 Mar 2012 by Evoluted New Media
Sabrina Chetcuti asks if plasma viscosity is replacing the widely used erythrocyte sedimentation rate test
Many laboratories have historically clung on to erythrocyte sedimentation rate (ESR) as a test to confirm that patients are unwell. Even though the science behind ESR is seen as dubious by laboratory scientists and many clinicians including consultant haematologists, why is the ESR still requested? Is it just out of habit that we continue to use a test that has no quality control (QC), producing results that will vary without any change in the patient’s condition? Aspirin and steroids are the backbone of many treatments for patients with inflammation, and yet they are the very drugs that will significantly interfere with ESR results, suggesting an improvement which may not have occurred.
Plasma viscosity (PV) testing was seen as the ‘cure’ for this habit more than 30 years ago, and yet this easy-to use, rapid and stable diagnostic tool has been overlooked by many laboratories as the high-volume alternative. Over the years, more and more laboratories have elected to use PV testing as a significant tool in their repertoire.
Some noteworthy centres of excellence, including Leeds General Infirmary, the Royal United Hospital Bath, Nobles Hospital on the Isle of Man, and the Royal Devon and Exeter, have made the ambitious commitment to eliminate ESR and replace it with PV.
Recently, the momentum for change appears to have taken significant steps forward in the laboratory drive for increased efficiency and modernisation, as more sites across the UK signal a sea change in breaking old habits around the use of ESR testing.
NHS Highland and Hull Royal Infirmary (HEY NHS Trust) are the latest trusts to have abandoned their ESR testing and replaced it with PV by working with their clinical community to drive that change. The laboratories took advantage of a reorganisation in haematology to overhaul the service and move to a more efficient system.
“You need to be able to get consistent results in order to provide useful data for the clinical community, and with PV we have internal and external QC (CQAS). Due to the excellent data CQAS provides and the total number of Benson analysers, the consistency is easily observable. The manual ESR system did not have its own QC and no external quality control was available,” said Mick Milner from NHS Highland.
These new sites have been able to provide some insight into how they achieved the change with the full support of their clinical colleagues. Together with the longer-term experiences of the Royal Devon and Exeter Hospital (RD&E), a process route map (Table 1) has been developed that can be followed by those laboratories that would also like to eliminate ESR testing, potentially reduce costs and provide the means to monitor acute phase inflammatory disease progression.
The Royal Devon and Exeter hospital managed to eliminate all ESR testing four years ago. Steve Walton (RD&E haematology laboratory manager) explained that the only area of difficulty was for one clinical trial. A drug used as part of a hip replacement procedure was only available following an ESR test result. This drug authorisation protocol is not routinely seen in arthritic hip replacement surgery. The orthopaedic surgeons and the microbiologists continue to use C-reactive protein (CRP) testing to check for the acute-phase inflammatory response in a two-stage process whereby the patient’s new hip is only inserted if there is no sign of infection. Once the critical phase is completed, PV testing is used for routine monitoring.
Similarly, NHS Highland rheumatologists used routine CRP testing to track patient progress with disease assessment scores and were able to eliminate ESR testing.
The consultation and support processes were handled as critical steps in reviewing the potential for moving away from ESR testing. NHS Highland consultant haematologist Dr Peter Forsyth drove the decision to make the change only after preparing the evidence base, where it was found that PV provided the laboratory with consistent, stable and reproducible data. This enables the requesting clinicians to plot disease progression with cumulative PV data.
The information was provided as part of a consultation involving the GPs and hospital consultants in order to discover what would happen if ESR testing was withdrawn. The overall view was that PV would provide a suitable alternative.
Forsyth said: “Having put a good evidence base together we found that PV gave us consistent data, it was easier, a separate specimen tube was not required, and additional financial savings could be made with increased numbers.”
Milner goes on to explain that education is critical. The clinicians require clear information on what a PV result means because the range appears limited. Compared with a wide ESR range (<8 mm to 120 mm), the PV normal range is narrow (1.50–1.72 mPa.s).
The laboratory has been posting additional information on its reports to assist clinical interpretation.
Time and sample transportation can provide significant challenges for any integrated system involving several laboratories and GP point-of-care services. The NHS Highland and HEY NHS trusts found that switching to PV testing helped them overcome difficulties in managing the return of samples from outlying clinics.
As one of the most important vehicles for communication and process improvement, the prospect of adverse feedback often causes some trepidation. Across all three trusts, the feedback received was very positive.
“There were a lot of glowing comments from the feedback questionnaires. The only complaint we received was that the turnaround time was now too quick – glowing praise indeed,” said Elaine Boyle, haematology service manager at Hull Royal Infirmary (HEY NHS Trust).
Since the early investigations into PV testing by Harkness1 in 1971, a number of research publications have compared ESR measurement and PV. The results are summarised by comparison of the potential for each technology to provide patient screening information (Table 2).
Both PV and ESR have been used to screen for the presence of infection or inflammation and to monitor disease activity. However, the significant differences between each test have led many haematology laboratories to make the case for change, both from a clinical and technical perspective. Over the past few years, significant evidence has emerged to show that more laboratories are increasing the momentum to make that change.
The author would especially like to thank Elaine Boyle (haematology service manager, HEY NHS Trust), Dr Peter Forsyth (consultant haematologist, NHS Highland), Mick Milner (haematology manager, NHS Highland) and Steve Walton (laboratory manager, RD&E) for their support in the production of this article.
References
- Harkness J. The viscosity of human blood plasma: its measurement in health and disease. Biorheology 1971; 8 (3): 171–93
- Ng T. Erythrocyte sedimentation rate, plasma viscosity and C-reactive protein in clinical practice. Br J Hosp Med 1997; 58: 521–3
- Brittain GPH, Mcilwaine GG, Bell JA, Gibson JM. Plasma viscosity or erythrocyte sedimentation rate in the diagnosis of giant cell arteritis. Br J Ophthalmol 1991; 75: 656–9
- Gudmundsson M, Nordborg E, Bengtsson B-A, Bjelle A. Plasma viscosity in giant cell arteritis as a predictor of disease activity. Ann Rheum Dis 1993; 532: 104–9
Contact: saby@bensonviscometers.com
This article was first published in Labmate UK and Ireland, in January 2012..
