August 19, 2024
When diagnosing inflammation, the physician almost automatically orders both tests. Although the Erythrocyte Sedimentation Rate (ESR) test is still in use, evil tongues say that its value is only to make it clear - the laboratory is working today.
How are these tests different? Should we use only C-reactive protein (CRP) nowadays?
CRP is able to attach to the polysaccharides of bacterial and fungal walls. Once attached, it acts as an opsonin, binding the complement component C1q and triggering the classical pathway of its activation without antibodies.
ESR - monitoring the process
In the case of ESR, it is not a matter of determining the amount of a single protein, but of observing the result of an entire process. ESR reflects the length of the plasma column in mm above the settled red blood cells of whole blood with anticoagulant after one hour of standing in a capillary under gravity. It is a cheap laboratory test and is often used as a general "sickness index" in conjunction with the clinical picture and physical examination
What will determine the value of the sedimentation rate?
ESR depends on the result of the interaction between the forces that promote erythrocyte sedimentation and the forces that counteract it.
Under conditions of free blood circulation, the negative charge of the erythrocyte membrane provided by sialic acid (z-potential) prevents the formation of aggregates. In the in vitro test, erythrocytes aggregate along one axis, and the weight of cells increases relative to the area of their contact with the formation of "coin columns" (rouleaux).
Not only inflammatory factors, but also non-inflammatory plasma proteins and erythrocyte characteristics not directly related to inflammation (shape, number of cells) influence ESR.
Elevated ESR
The positive charge of acute-phase proteins and class M immunoglobulins on the erythrocyte surface can overcome the repulsive effect of the negative z-potential and increase the rate of cell sedimentation.
This is observed, for example, in diseases accompanied by an increase in fibrinogen production (pregnancy, infections, diabetes, the last stages of renal failure, heart disease, tumors)
ESR increases with age and is slightly higher in women.
A marked increase in ESR (> 100 mm/hour) may be caused by infections, multiple myeloma, Waldenström macroglobulinemia, temporal arteritis or polymyalgia rheumatica. In general, it is observed that an extremely high erythrocyte sedimentation rate is characteristic primarily of infections, followed by → connective tissue diseases and then → metastatic tumors. CRP probably follows this pattern as well.
ESR and CPR in dynamic
Although both CRP and ESR are related to biomarkers of inflammation, but patterns of response are different.
Start inflammation - onset time
Fall after resolution of inflammation
Thus, CRP is a more sensitive marker of the acute phase of inflammation at the onset of inflammation than ESR.
Although in the majority of cases there is a simultaneous increase in CRP and PSA, but in 10-20% of cases there is multidirectionality in the results, and it is not always due to different response rates.
Discordance between CRP and ESR values
Tissue damage (infarction, thromboembolism) can result in a high CRP - normal ESR. This may be because CRP may simply not respond to minor inflammation.
On the other hand, in a tumor without inflammation, the CRP may be only slightly elevated and the ESR may respond significantly. (for example in myeloma ).
But let us return to the topic of this article - inflammation.
Despite the obvious advantages of CRP, ESR can be an independent value in the diagnosis and monitoring of some diseases when high ESR and normal (moderately elevated) CRP are noted.
- Osteomyelitis and its early complication with infection, including in prosthetic
joints. A possible explanation of this could be low-level pathogens such as coagulase negative Staphylococci. - Systemic lupus erythematosus (SLE) and other collagenoses, especially if there was no elevation of CRP in previous exacerbations. A possible explanation for this could be the suppression of ESR production by interferon (interferon-alpha) by hepatocytes.
At the same time, the increase of ESR in the same cases may help in diagnosing the accession of bacterial infection and serositis.
Thus, ESR and CRP, being both markers of inflammation, do not have specificity that would allow to distinguish the nature of the inflammatory reaction. Given that CRP reacts more quickly, physicians often favor this test in diagnosing beginning and monitoring ongoing inflammation.
Often both tests are performed at the same time, but in some countries there are recommendations for a more selective approach to the tests. In this case, it is recommended to start with the determination of CRP, and ESR is not considered a routine test. However, in some (few) situations, it may be necessary to perform a ESR test.