CRP — Normal Range & Interpretation

Clinical Context

C-reactive protein is an acute-phase reactant produced by the liver in response to interleukin-6 released during tissue injury, infection, or inflammation. It rises within 6 to 8 hours of an inflammatory stimulus and peaks around 48 hours, making it a sensitive but nonspecific marker of systemic inflammation. NPs use CRP to detect active disease, monitor treatment response, and assess cardiovascular risk when ordered as high-sensitivity CRP.

Elevated CRP accompanies bacterial infection, rheumatoid arthritis flares, inflammatory bowel disease, vasculitis, malignancy, trauma, burns, and postoperative states. Mildly elevated high-sensitivity CRP reflects low-grade vascular inflammation and correlates with increased coronary artery disease risk. Obesity, smoking, and diabetes also raise baseline CRP. Low or undetectable CRP indicates absence of significant acute inflammation and helps rule out bacterial processes when clinical suspicion is low.

High-yield for NP boards: CRP is an acute-phase reactant that rises faster and falls faster than ESR, making it the preferred marker for tracking treatment response in conditions like rheumatoid arthritis and osteomyelitis. Expect questions distinguishing standard CRP from hs-CRP for cardiovascular risk stratification, and scenarios where CRP trends guide antibiotic duration or flare assessment. Know that CRP lacks specificity and requires correlation with the full clinical picture.

Related Labs

• HbA1c — %
• ESR — mm/hr
• hs-CRP — mg/L
• Uric Acid — mg/dL
• Iron (serum) — μg/dL

Sources

• MedlinePlus
• ARUP Consult