When your doctor suspects inflammation — from infection, autoimmune disease, tissue injury or malignancy — they don't rely on a single marker. The inflammation response is complex and different markers reflect different aspects of it, at different times.
CRP (C-reactive protein)
CRP is produced by the liver within 6–12 hours of an inflammatory trigger and falls rapidly when the cause resolves. It's useful for detecting acute inflammation and monitoring response to treatment. A high-sensitivity CRP (hs-CRP) below 1 mg/L suggests low cardiovascular risk; above 3 mg/L is high risk.
ESR (erythrocyte sedimentation rate)
ESR measures how quickly red blood cells settle in a tube. It rises more slowly than CRP (over days) and falls more slowly too. It's less specific than CRP but useful for monitoring chronic inflammatory conditions — rheumatoid arthritis, vasculitis, polymyalgia rheumatica — where long-term trends matter.
Ferritin as an inflammation marker
Ferritin is primarily an iron-storage protein, but it's also an acute-phase reactant — it rises with inflammation and infection, independently of iron stores. A very high ferritin (above 500–1000 µg/L) in the absence of iron overload suggests significant systemic inflammation, malignancy or — at extremely high levels — conditions like haemophagocytic lymphohistiocytosis (HLH) or Adult Still's disease.
Procalcitonin and interleukin-6
- Procalcitonin — rises specifically in bacterial infections (not viral); used to guide antibiotic decisions and monitor response to treatment in sepsis
- Interleukin-6 (IL-6) — a key cytokine in the inflammatory cascade; used in monitoring conditions like rheumatoid arthritis and cytokine release syndrome (e.g. in cancer immunotherapy)