What labs indicate inflammation?

Laboratory Tests Indicating Inflammation

The core inflammatory laboratory panel consists of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), complete blood count with differential, and a complete metabolic panel, with CRP being the preferred acute-phase marker due to superior standardization and faster response to disease activity. 1

Tier 1 Screening Tests

Initial inflammatory workup should include:

• Complete blood count (CBC) with manual differential to identify lymphopenia, neutrophilia, thrombocytopenia, leukocytosis, or anemia 2, 1
• C-reactive protein (CRP) is the preferred acute-phase reactant with acceptable precision down to 0.3 mg/L and better correlation with acute disease activity than ESR 1
  • CRP >5-6 mg/L indicates inflammation with 73% sensitivity and 78% specificity for organic disease 2
  • CRP >10-20 mg/dL is commonly seen in significant inflammatory conditions 2
• Erythrocyte sedimentation rate (ESR) with cutoffs >20 mm/h in men and >30 mm/h in women indicating elevation 1
  • Moderate elevation (50-100 mm/h) indicates significant underlying disease 1
  • ESR has 54-78% sensitivity and 46-95% specificity at cutoffs of 10-15 mm/h 2
• Complete metabolic panel including sodium, potassium, glucose, creatinine, liver enzymes (AST, ALT), and albumin to identify hyponatremia, hypoalbuminemia, azotemia, and hepatic involvement 2, 1

Extended Inflammatory Markers

When initial screening suggests inflammation, consider:

• Ferritin typically ranges 500-2,000 ng/dL in inflammatory conditions, though levels <30 μg/L indicate iron deficiency without inflammation 1
  • In the presence of active inflammation, ferritin up to 100 μg/L may still represent iron deficiency 1, 3
• D-dimer is frequently elevated in systemic inflammatory states 1
• Lactate dehydrogenase (LDH) serves as a marker of tissue damage and inflammation 1
• Procalcitonin can be profoundly elevated in inflammatory conditions even without bacterial infection 1
• Fibrinogen is an acute-phase reactant with acceptable precision, though less favored than CRP for routine use 1
• Serum albumin and pre-albumin assess nutritional status and degree of inflammation, particularly in chronic inflammatory conditions 1, 3

Organ-Specific Inflammatory Testing

For cardiac involvement:

• Troponin T and BNP/NT-proBNP are essential when cardiac involvement is suspected, though BNP is an acute-phase reactant and may be elevated in inflammatory conditions without cardiac disease 2, 1

For intestinal inflammation:

• Fecal calprotectin is the most sensitive non-invasive marker for intestinal inflammation 2, 3
• Fecal lactoferrin can also assess intestinal inflammation, though to a lesser degree than calprotectin 2
• Stool cultures and C. difficile toxin testing should be performed to exclude infectious causes 2, 3

Critical Interpretation Caveats

ESR has multiple confounders:

• Anemia, azotemia, elevated immunoglobulins, rheumatoid factor, female sex, and advancing age all increase ESR independent of inflammatory activity 1
• ESR has a longer half-life than CRP, making it more useful for monitoring chronic inflammatory conditions 4

CRP limitations:

• Normal CRP levels do not exclude active inflammation, particularly in ulcerative colitis where some patients have active disease without CRP elevation 1, 3
• CRP is more useful in acute inflammatory conditions and responds more quickly to therapy than ESR 4, 5

CRP/ESR discordance occurs in approximately 12% of patients:

• High CRP/low ESR suggests acute infections (urinary tract, gastrointestinal, pulmonary, bloodstream) or acute thrombotic events 6
• High ESR/low CRP suggests connective tissue diseases (systemic lupus erythematosus), bone/joint infections, or ischemic stroke 6

Monitoring Strategy

For persistent or unexplained elevation:

• Repeat ESR and CRP in 2-4 weeks to determine if elevation is persistent or transitory 1

During active inflammatory disease:

• Monitor ESR every 1-3 months until remission is achieved, then every 3-6 months once low disease activity is maintained 1