Inflammatory Markers
CRP increases within hours, peaks within 48hrs, and resolves within
3-7days
ESR increases slowly and can remain elevated for weeks
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CRP and ESR widely used diagnostic tests for detecting inflammatory
conditions: infection, autoimmune disorders, malignancies, or tissue
necrosis
"The CRP test measures the level of a plasma protein (C-reactive
protein) produced by liver cells in response to acute inflammation
or infection. Unlike CRP, which is a direct measure of inflammatory
response, ESR (erythrocyte sedimentation rate) is an indirect
measure of the level of inflammation in the body. ESR measures the
rate at which red blood cells settle in a specially designated tube
of anticoagulated blood, an effect that is altered by proteins
associated with an inflammatory response...
CRP rises within hours of onset of an infection or
inflammatory condition and returns to normal within three to seven
days if the acute process is resolved.
ESR, on the other hand, increases in a slower manner and
remains elevated for a longer period of time (weeks). In
addition, ESR is a non-specific measure that can be affected by
factors other than inflammation, such as the size, shape, and number
of red blood cells; levels of serum fibrinogen and immunoglobulins;
renal function; age and sex; pregnancy; and use of medications."
There are only two circumstances where the erythrocyte sedimentation
rate is superior – detecting low-grade bone and joint infections,
and monitoring disease activity in systemic lupus erythematosus.
Because of these differences, CRP testing is often chosen over ESR
in the assessment of early inflammation; however, there is no
consensus on which single test is preferred and as a result,
physicians often request both tests. "
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ESR > 100 should prompt evaluation for severe infection,
malignancy, and connective tissue disorders
Pediatric IBD typically would have an ESR in the range of 20 -
70 mm/hr
References:
https://www.ncbi.nlm.nih.gov/books/NBK333366/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4653962/