How should follow-up serum C-reactive protein (CRP) in patients with community-acquired pneumonia (CAP) be interpreted?

CRP level should drop to less than one-half of its value on admission after a couple of days of antibiotic therapy, since CRP half-life is less than a day following zero order elimination kinetics. 
Of interest, in a study of serial CRP in severe CAP (1), a CRP ratio >0.5 by day 3 was associated with non-resolving pneumonia ( sensitivity 91%, specificity 55%)   performing significantly better than body temperature or WBC count.  
So if there is any doubt about how a patient is doing clinically, a repeat CRP looking for a drop of greater than on-half after 3-4 days of therapy may be helpful.

 

Bonus Pearl: Did you know that the half-life of CRP is 19 h?

If you liked this pearl, sign up under MENU and catch future fresh pearls straight into your mailbox!

 

Reference

1. Coelho L, Povoa P, Almenda E, et al. Usefulness of C-reactive protein in monitoring the severe community-acquired pneumonia clinical course.  Critical Care 2007;11:R92 https://ccforum.biomedcentral.com/articles/10.1186/cc6105

 


 

How should follow-up serum C-reactive protein (CRP) in patients with community-acquired pneumonia (CAP) be interpreted?

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.