The C-reactive protein (CRP) test is a crucial diagnostic tool used to detect inflammation that may arise from various conditions such as infections or autoimmune diseases like rheumatoid arthritis or inflammatory bowel disease. This test measures the concentration of CRP, a protein produced by the liver and released into the bloodstream. Infections and inflammation can cause CRP levels to fluctuate, with elevated levels often indicating an acute phase of inflammation.

The erythrocyte sedimentation rate (ESR) and CRP are frequently measured together, particularly in infectious states. New evidence indicates that CRP is a valuable marker for serious bacterial infections, especially in neonates, as CRP is not transferred across the placenta and thus signifies neonatal production. Consequently, measuring CRP levels in infants at risk for infection is recommended by some groups.

Both ESR and CRP levels are non-specific markers of inflammation, and while not specific to rheumatoid arthritis (RA), they are utilized to assess disease activity. Elevated results, barring other causes such as infection, suggest that the disease is highly active. Varied CRP levels can be attributed to multiple factors. For instance, an individual may exhibit significantly different readings in the high-sensitivity CRP test (hsCRP) at different times, which could be unrelated to cardiovascular risks if cholesterol levels and cardiac evaluations are normal.

Inflammation is the immune system’s response to injury or infection. Acute infections, such as influenza or pneumonia, and chronic conditions like post-herpetic neuralgia—an aftermath of shingles—can also raise CRP levels.

Procalcitonin (PCT) levels, which increase rapidly in response to bacterial infection, offer a contrast to CRP levels. PCT levels rise within 2-4 hours and may peak after 6-12 hours, whereas CRP levels take about 12-24 hours to rise and 48 hours to peak. Moreover, CRP is not as specific to bacterial infections and can be influenced by parasitic diseases like malaria and chronic infections such as tuberculosis and leprosy.

For further information, references are available through links to authoritative sources: C-Reactive Protein (Blood) – University of Rochester Medical Center, The Erythrocyte Sedimentation Rate and CRP, Understanding Rheumatoid Arthritis Lab Test Results | HSS, and Harvard Health – Post-herpetic Neuralgia and CRP.

This overview addresses the various aspects of CRP levels, their implications, and the conditions that can affect them, providing a comprehensive understanding for patients and healthcare providers alike.