The ESR or CRP—An Old Debate Flares Up
Abstract & Commentary
Synopsis: The erythrocyte sedimentation rate (ESR) is affected by so many extrinsic factors that its clinical usefulness is severely compromised.
Source: Jurado RL. Why shouldn’t we determine the erythrocyte sedimentation rate? Clin Infect Dis. 2001;33:548-549.
The erythrocyte sedimentation rate (ESR) is a nonspecific screening test for various inflammatory diseases and has a long and venerable history. The test requires blood to be drawn and collected in citrate or EDTA as anticoagulant, is quick and inexpensive, and usually offered as part of the basic service. Although simple to perform, the ESR is the result of a complex biological process dependent upon the amount of fibrinogen (also an acute-phase reactant) and the degree to which red blood cells aggregate, which in turn depends upon the physical properties of the surface including free energy, charge, and dielectric constant.
Besides elevated concentrations of fibrinogen, the ESR is also increased by a variety of factors and reduced by others (see Table).
|Table: Factors Other Than the Concentration of Fibrinogen That Affect the ESR|
|Cause elevation of ESR||Cause reduction in ESR|
|Anemia||Morphological abnormalities of the red blood cells|
|Increased concentrations of other proteins including M-protein, macroglobulins, and RBC agglutinins||Polycythemia|
|Renal failure||High white blood cell count|
|High blood cholesterol||High serum concentrations of bile salts that affect red blood cell membranes|
|Extreme obesity||Congestive heart failure|
|Female gender||Valproic acid|
|Advanced age||Low molecular weight dextrans|
|Tilting the tube||Cachexia|
|High temperature||Low temperature|
|Delay > 2 h before testing|
By contrast, the acute-phase reactant C-reactive protein (CRP) is not affected by any of these factors and is regarded as a better alternative for gauging the intensity of the inflammatory response and for providing a better means of monitoring. However, ESR is still preferred by some because, although CRP might be a better test, it requires specialized technology making it less widely available, takes longer to do, and is more expensive. Jurado dismisses these arguments claiming that those who still insist on using the ESR only do so because of their adherence to tradition and not because of science or logic.
Comment by J. Peter Donnelly, PhD
It may seem strange that this article should appear at this time in an infectious diseases journal, especially as the ESR has long given way to CRP in this area. However, while microbiologists and infectious disease physicians might be convinced that this debate (which has raged since the mid-1960s) has long been settled, other clinical specialists clearly think otherwise. Indeed, only recently a study was done among patients with solid tumors and lymphomas to investigate the possibility of using the ESR and CRP for differentiating neoplastic fever from infectious fever and concluded that neither was useful.1
Ironically, although CRP is a more specific acute-phase reactant than ESR, it still has to find its proper place in the clinic. After all, like the ESR, an elevated CRP level only reflects active inflammation but sheds no light upon the etiology. Its clinical use also depends upon the context and its ability to increase or lower diagnostic probabilities. Taken in isolation and without a clear purpose, neither the ESR nor CRP for that matter will be anything but a waste of time and money.
1. Kallio R, et al. C-reactive protein and erythrocyte sedimentation rate in differential diagnosis between infections and neoplastic fever in patients with solid tumors and lymphomas. Support Care Cancer. 2001; 9:124-128.
Peter Donnelly, Clinical Microbiologist, University Hospital, Nijmegen, The Netherlands, is Associate Editor of Infectious Disease Alert.