Inflammation is the body’s natural response to infection, injury or irritation. When inflammation occurs, the immune system releases white blood cells and other chemicals into the bloodstream to protect the body against foreign substances. While some inflammation is normal, high levels of inflammation can indicate an underlying health condition. Blood tests that measure inflammatory markers in the blood can help identify and monitor inflammatory conditions.
C-Reactive Protein (CRP)
C-reactive protein (CRP) is a protein produced by the liver in response to inflammation. CRP levels in the blood rise rapidly in response to inflammation from infection, injury or chronic conditions. A high CRP level indicates there is inflammation somewhere in the body. Normal CRP levels are generally below 10 mg/L, while levels above this can signify:
- Bacterial infections
- Viral infections
- Inflammation of tissues
- Autoimmune disorders like lupus or rheumatoid arthritis
- Inflammatory bowel disease
- Heart attack or stroke risk
CRP levels can rise for numerous reasons, so an elevated CRP alone does not point to a specific diagnosis. However, it can indicate the presence of inflammation and prompt further testing. Treating the underlying inflammatory condition can help bring CRP levels back to normal.
Erythrocyte Sedimentation Rate (ESR)
The erythrocyte sedimentation rate (ESR) test measures how quickly red blood cells settle at the bottom of a test tube over a set time. During inflammation, the blood levels of certain proteins like fibrinogen increase. These proteins cause red blood cells to stick together and settle more rapidly. A faster than normal settling rate indicates increased levels of inflammation. Normal ESR ranges are:
- Adult men younger than 50 years: 0–15 mm/hour
- Adult men older than 50 years: 0–20 mm/hour
- Adult women younger than 50 years: 0–20 mm/hour
- Adult women older than 50 years: 0–30 mm/hour
An elevated ESR can signify inflammation from:
- Infections
- Cancers like lymphoma or multiple myeloma
- Autoimmune diseases
- Inflammatory conditions like vasculitis
- Heart disease
- Kidney disease
- Rheumatologic diseases
While ESR is a very non-specific marker of inflammation, tracking changes in a person’s ESR over time can help monitor diseases and response to treatments.
Complete Blood Count (CBC)
A complete blood count (CBC) test measures different components of the blood. While a CBC does not directly measure inflammation, it can provide clues about inflammatory conditions. For example:
- High white blood cell count – An elevated number of white blood cells beyond the normal range can indicate the body is fighting an infection and releasing white blood cells in response to inflammation.
- High neutrophil percentage – Neutrophils are a type of white blood cell that increases during bacterial infections and inflammation. A higher neutrophil percentage indicates the immune system is actively fighting inflammation.
- Low red blood cell, hemoglobin and hematocrit – Inflammation can suppress red blood cell production and lead to anemia. Low levels of RBCs, hemoglobin and hematocrit can be seen with some chronic inflammatory diseases.
- High platelet count – Platelets participate in the inflammatory response. Increased platelets can occur with inflammatory conditions like infections, autoimmune disorders and cancers.
Other CBC changes that can indicate inflammation:
| CBC Component | Inflammatory Changes |
|---|---|
| Mean corpuscular volume (MCV) | Lower MCV can occur with inflammation-driven anemia |
| Mean corpuscular hemoglobin (MCH) | Lower MCH can occur with inflammation-driven anemia |
| Red cell distribution width (RDW) | Higher RDW can occur with inflammation-driven anemia |
While CBC results can point towards inflammation, they are not definitive. CBCS should be interpreted in combination with inflammatory markers like CRP and clinical signs and symptoms.
Ferritin
Ferritin is a protein in the body that binds and stores iron. It also has roles in inflammation and immunity. Low ferritin levels can indicate iron deficiency. High ferritin levels often signify increased inflammation, especially when iron levels are normal. Elevated ferritin can occur with:
- Liver disease
- Infections
- Cancer
- Autoimmune conditions like rheumatoid arthritis
- Kidney failure
- Heart disease
Testing iron levels along with ferritin can help determine if high ferritin is due to iron overload rather than inflammation. Treating the underlying condition can help lower ferritin to normal ranges.
Fibrinogen
Fibrinogen is a clotting factor that helps stop bleeding. During inflammation, the liver releases more fibrinogen into the bloodstream. This makes blood clot faster. High fibrinogen levels can indicate inflammation present with:
- Infections
- Injuries or trauma
- Cancers
- Autoimmune disorders
- Heart disease
- Stroke
Testing fibrinogen along with other inflammatory markers can help identify the source of inflammation when elevated.
Albumin
Albumin is a protein made by the liver that carries hormones, enzymes and other substances in the blood. Inflammation can lower albumin production. Low blood albumin levels can occur with:
- Kidney and liver disease
- Malnutrition and malabsorption
- Severe injury or infection
- Gastrointestinal disease
- Cancer
Low albumin correlates with higher levels of CRP and other markers of inflammation. Treating the cause can help restore normal albumin levels.
Neutrophil Gelatinase-Associated Lipocalin (NGAL)
Neutrophil gelatinase-associated lipocalin (NGAL) is released by immune cells like neutrophils during inflammation. High NGAL levels are linked to inflammation resulting from:
- Kidney injury
- Heart disease
- Bowel diseases
- Cancers
- Lupus
- Infections
NGAL testing is still being researched for its role in detecting early kidney damage and guiding treatment. Elevated NGAL warrants further diagnostic testing.
Interleukin-6 (IL-6)
Interleukin 6 (IL-6) is an immune signaling molecule called a cytokine that is released early on during inflammation. IL-6 levels in the blood can rise sharply with inflammation before other biomarkers like CRP. High IL-6 can indicate inflammation and immune activation due to:
- Bacterial, viral and fungal infections
- Rheumatoid arthritis
- Inflammatory bowel disease
- Lupus
- Cancers like multiple myeloma
IL-6 testing is still primarily used in research but holds promise for detecting and monitoring some inflammatory and autoimmune conditions.
Tumor Necrosis Factor Alpha (TNF-α)
Tumor necrosis factor alpha (TNF-α) is an inflammatory signaling cytokine released by immune cells during acute and chronic inflammation. Excess TNF-α production is linked to inflammatory diseases like:
- Rheumatoid arthritis
- Psoriasis
- Crohn’s disease
- Ulcerative colitis
- Ankylosing spondylitis
Drugs that block TNF-α are used to treat these conditions. Testing levels of TNF-α can help diagnose inflammatory illnesses and monitor treatment response.
Conclusion
Inflammation is a normal immune response, but excessive inflammation can lead to chronic disease over time. Blood tests that measure inflammatory proteins, immune cells and related markers can help uncover the presence of inflammation and guide diagnosis and treatment. Working with your doctor to identify and treat any sources of inflammation through lifestyle changes, medications or other interventions can improve your overall health.