Read on Twitter
After struggling with some @CPSolvers cases and having a case of ESR/CRP negative GCA @IMResidencyDuke, I wanted to dive deeper into ESR and CRP to interpret them better. Thanks to @kidney_boy for tweetorial pointers. (1/x)
ESR and CRP are part of the acute phase response (APR). One of the most important components of the APR is acute phase proteins (APP), but what are these proteins? (2/x)
An APP is any protein whose plasma concentration increases or decreases by at least 25% during stress. (3/x) https://pubmed.ncbi.nlm.nih.gov/6953917/
APPs have been found in infections, traumas, burns, inflammatory conditions, and advanced cancer. These proteins are regulated by multiple cytokines, including IL-6, IL-1β , TNF-α , interferon-γ , and TGF-β. (4/x) https://pubmed.ncbi.nlm.nih.gov/9971870/
Pop quiz. Which of these APPs are seen in the highest concentrations during an acute phase response? (5/x)
CRP!
From this study, we can see that some APPs such as CRP and serum amyloid A can increase over 1000-fold in times of stress. We can also see that albumin is a negative acute phase reactant and actually decreases. (6/x)
https://pubmed.ncbi.nlm.nih.gov/9971870/
From this study, we can see that some APPs such as CRP and serum amyloid A can increase over 1000-fold in times of stress. We can also see that albumin is a negative acute phase reactant and actually decreases. (6/x)
https://pubmed.ncbi.nlm.nih.gov/9971870/
So what is C-Reactive Protein (CRP)? Originally discovered in 1930, C-Reactive Protein reacted to the C-polysaccharide in the acute phase of pneumococcus pneumonia. (7/x) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2131884/
CRP’s major function is to activate the innate immune system. As we saw above, serum concentrations of CRP can rapidly increase and decrease in response to inflammation. (8/x)
And ESR? The erythrocyte sedimentation rate is how fast red blood cells fall in a test tube. How does this relate to inflammation? The answer is fibrinogen. (9/x)
As in the figure above, fibrinogen is also an APP. With increased fibrinogen there is increased cohesion of red blood cells resulting in increased density. This “pellet” falls faster, increasing the sedimentation rate leading to a higher ESR.(10/x) https://pubmed.ncbi.nlm.nih.gov/11462193/
Problems with RBCs can make the ESR inaccurate. Anemia, increasing age, obesity, and renal disease all increase the ESR. Factors that decrease ESR include low fibrinogen states, polycythemia, and morphologic abnormalities in the red blood cells. (11/x) https://pubmed.ncbi.nlm.nih.gov/11462193/
There is a correction for ESR by age from a 1983 study with ~ 27,000 men and ~ 1,000 women. ESR correction for women = (age in years + 10)/2. ESR correction for men = (age in years)/2 . (12/x)
https://pubmed.ncbi.nlm.nih.gov/6402146/
https://pubmed.ncbi.nlm.nih.gov/6402146/
Take home points!
1. CRP is an APP that can change rapidly in response to inflammation.
2. A discrepancy between ESR and CRP maybe due to different cytokine responses or due to the multiple confounders of ESR. (13/x)
1. CRP is an APP that can change rapidly in response to inflammation.
2. A discrepancy between ESR and CRP maybe due to different cytokine responses or due to the multiple confounders of ESR. (13/x)
