Systemic immune-inflammation index (SII)
Immune system healthAlso known as: immune-inflammation index, Immun-Entzündungs-Index, systemischer Immun-Entzündungs-Index
SII integrates neutrophil, platelet, and lymphocyte counts into a single measure of immune and inflammatory status.
Reference range
Source: Ahead Health benchmark
Reference ranges may vary between labs and assays. Always interpret results with your healthcare provider.
Why this matters
SII provides superior prognostic value compared to simpler ratios by incorporating platelet-mediated inflammation. Elevated SII predicts poor outcomes in cancer, cardiovascular disease, and severe infections.
How this connects to other biomarkers
- SII (Thrombocytes (Platelets) × Neutrophils (abs.) / Lymphocytes (abs.)) integrates three immune-inflammatory cell lines into a single prognostic marker.
- Elevated SII reflects active inflammation with reactive thrombocytosis and is associated with worse outcomes in cardiovascular disease, cancer, and infection.
- Use alongside NLR (Neutrophils/Lymphocytes) and Systemic Inflammation Response Index (SIRI) for a fuller integrated read.
How often should I test Systemic immune-inflammation index (SII)?
Most adults benefit from yearly SII reassessment as part of a CBC with differential.
At baseline / for screening: Once every 12 months from age 30 as part of a CBC with differential. More frequently if you have a chronic inflammatory condition.
When monitoring an intervention or change: These ratios are tracked alongside the CBC rather than on their own cadence. Retest with your next CBC after a sustained anti-inflammatory lifestyle change (better sleep, weight loss, Mediterranean-style diet). Single values are sensitive to acute illness, recent exercise, and stress, so test under consistent conditions.
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