What is the Difference Between CRP and SED Rate?

C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are both blood tests used to measure inflammation in the body. However, there are some differences between the two tests:

1. Sensitivity and specificity: CRP is considered a better indicator of inflammation than ESR, as it is more sensitive and responds more quickly to changes in the clinical situation. ESR, on the other hand, 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.
2. Response time: CRP rises within hours of the onset of an infection or inflammatory condition and returns to normal more quickly than ESR, which increases in a slower manner and remains elevated for a longer period of time.
3. Circumstances of use: There are two circumstances where ESR is superior to CRP: detecting and monitoring disease activity in systemic lupus erythematosus (SLE) and some low-grade bone and joint infections (e.g., joint prosthesis infections due to low-level pathogens such as coagulase-negative staphylococci).
4. Concordance: CRP and ESR are likely to yield concordant results 67% to 81% of the time. However, patterns of response are different for each test, and CRP is often chosen over ESR in the assessment of early inflammation.

In summary, CRP is generally considered a more sensitive and accurate reflection of the acute phase of inflammation than ESR. However, ESR may be more suitable in specific circumstances, such as detecting and monitoring disease activity in SLE or certain low-grade bone and joint infections.

Comparative Table: CRP vs SED Rate

CRP (C-reactive protein) and SED rate (erythrocyte sedimentation rate) are both blood tests used to diagnose inflammation, but they differ in terms of sensitivity, specificity, and response time to changes in the clinical condition. Here is a table summarizing the differences between CRP and SED rate:

CRP is considered a better and more sensitive indicator of inflammation compared to SED rate. Additionally, CRP responds more quickly to changes in the clinical situation, making it a more reliable marker for monitoring treatment effectiveness.