Systemic immune-inflammation index (SII)
InflammationAlso 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
| Level | Range |
|---|---|
| High | above 655 |
| Normal | to 655 |
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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