Is it helpful to repeat C-Reactive Protein (CRP) testing?

From the Guidelines

Repeating CRP tests is not recommended unless there is a clear clinical indication, such as monitoring response to treatment for inflammatory conditions or infections, as stated in the guidelines by the Centers for Disease Control and Prevention and the American Heart Association 1.

Clinical Indications for Repeating CRP

• Monitoring response to treatment for inflammatory conditions, infections, or autoimmune diseases
• Evaluating disease activity and treatment response in chronic inflammatory conditions like rheumatoid arthritis
• Assessing treatment effectiveness in bacterial infections

Timing of Repeat Testing

• For bacterial infections, repeating CRP every 24-48 hours can help assess treatment effectiveness
• For chronic inflammatory conditions, periodic measurements (every 1-3 months) help evaluate disease activity and treatment response

Importance of Clinical Judgment

• The decision to repeat CRP tests should be based on clinical judgment and the specific condition being monitored
• Unnecessary repeated testing should be avoided when clinical improvement is evident or in conditions where CRP isn't a reliable marker, as recommended by the American College of Cardiology/American Heart Association 1

Quality of Evidence

• The guidelines from the Centers for Disease Control and Prevention and the American Heart Association provide a Class I recommendation for the use of hs-CRP as an independent predictor of increased coronary risk, but the evidence for repeating CRP tests is limited to specific clinical situations 1

From the Research

Repeating CRP Tests

• Repeating CRP tests can be helpful in certain situations, such as detecting inflammatory bursts in patients with acute bacterial infections presenting with a first relatively low CRP 2.
• A second CRP test taken within 12 hours from the admission CRP test can serve as an important tool to identify patients with an evolving inflammatory burst commonly seen during acute bacterial infection 2.
• CRP trajectories significantly differ based on infection type and antibiotic treatment, and frequent CRP measurement could be a valuable diagnostic and risk stratification tool in hospitalized patients 3.

CRP-Guided Antibiotic Use

• The use of CRP-based algorithms seems to reduce antibiotic treatment duration in neonates, as well as to decrease antibiotic treatment initiation in adult outpatients 4.
• CRP-guided protocols can reduce the total amount of time required for antibiotic therapy when compared to standard protocols of treatment in hospitalized patients with acute bacterial infection 5.
• However, further high-quality studies are still needed to assess safety, particularly in children outside the neonatal period 4.

Clinical Applications

• CRP measurement is widely used for the diagnosis and monitoring of inflammatory conditions, including sepsis, trauma, and malignancies 6.
• CRP has been proposed to guide the use of antibiotics, and its measurement can help identify patients with significant bacterial infections 2, 4, 5.