SII (Systemic Immune-Inflammation Index)

A composite inflammation-immunity index with strong oncology evidence.

What it is

SII is calculated as (Platelets × Neutrophils) ÷ Lymphocytes. It combines three blood count components into a single index that reflects the balance between pro- and anti-inflammatory states more comprehensively than NLR alone.

Why it matters

SII has shown strong prognostic value across multiple cancer types in the research literature, often outperforming NLR and CRP as a predictor of treatment outcomes and overall survival. A falling SII over treatment cycles is a favourable sign.

How to test

Calculated from full blood count: (PLT × NEUT#) ÷ Lymph#.

This information is for educational purposes only. Always discuss testing and interpretation of results with your care team.

Optimal range

Below 600

favourable

600–1200

borderline

Above 1200

elevated — poor prognostic signal

How often

Each blood count panel. Track trend over treatment cycles.