Is C-reactive protein (CRP) elevated in meningitis?

From the Guidelines

Yes, C-reactive protein (CRP) is typically elevated in meningitis, particularly in bacterial meningitis, with levels often rising significantly within 24-48 hours of infection onset. CRP is an acute-phase protein produced by the liver in response to inflammation, and meningitis—inflammation of the membranes surrounding the brain and spinal cord—triggers this inflammatory response. According to a study published in 2016 1, serum concentrations of CRP are highly discriminatory between pediatric bacterial and viral meningitis, with a sensitivity of 93% and a specificity of 100% when CRP levels are above 40 mg/L.

Key Points to Consider

• In bacterial meningitis, CRP levels often rise significantly, usually above 100 mg/L, within 24-48 hours of infection onset 1.
• Viral meningitis may cause more modest CRP elevation, but the degree of CRP elevation may help differentiate bacterial from viral causes, with higher levels suggesting bacterial infection 1.
• CRP levels typically decline with effective treatment, making it valuable for monitoring therapeutic response in meningitis cases.
• While CRP is a useful marker of inflammation, it is not specific to meningitis alone and must be interpreted alongside other clinical findings and tests such as lumbar puncture results, blood cultures, and neurological examination 1.

Clinical Application

In clinical practice, CRP levels can be used to support the diagnosis of bacterial meningitis, particularly when other tests such as CSF culture and Gram stain are negative or pending. However, it is essential to consider other potential causes of elevated CRP levels, such as sepsis or pneumonia, and to interpret CRP results in the context of the patient's overall clinical presentation. As noted in a study published in 2004 1, measurement of serum CRP concentration may be helpful in patients with CSF findings consistent with meningitis, but for whom the Gram stain result is negative and the physician is considering withholding antimicrobial therapy.

From the Research

CRP Levels in Meningitis

• CRP levels are often raised in patients with bacterial meningitis, with one study finding that an S-CRP value above 50 mg/l usually indicates bacterial etiology 2.
• In patients with viral meningitis, CRP levels are typically lower, with only 10% of patients having S-CRP concentrations above 50 mg/l 2.
• The discriminatory level for S-CRP to distinguish between bacterial and viral meningitis is 20 mg/l for children younger than 6 years of age, and 50 mg/l for older patients 2.

Relationship Between CRP and Inflammatory Markers

• Studies have shown that high serum concentrations of CRP are associated with higher levels of inflammatory markers, such as fibrinogen and neutrophils, in patients with bacterial meningitis 3, 4.
• CRP detection in serum in the acute phase of central nervous system infection is diagnostically important, as it suggests a purulent process 4.

Diagnostic Value of CRP

• Testing of CSF for CRP is a simple, rapid, and accurate method for the laboratory diagnosis of bacterial meningitis, with a sensitivity of 97% and specificity of 98% 5.
• CRP levels in CSF can be used to distinguish between bacterial and viral meningitis, particularly in areas lacking adequate laboratory facilities 5.