Systemic immune-inflammation index as a prognostic biomarker in critically ill dogs

Area of Science:

• Veterinary Medicine
• Critical Care
• Immunology

Background:

• Assessing prognosis in critically ill dogs with systemic inflammation is challenging.
• The Systemic Immune-Inflammation Index (SII), a biomarker in human medicine, has unclear relevance in veterinary critical care.
• This study evaluates the clinical significance and reference interval of SII in dogs.

Purpose of the Study:

• To evaluate the clinical significance of the Systemic Immune-Inflammation Index (SII) in critically ill dogs.
• To establish a reference interval for SII in healthy control dogs.
• To assess SII's accuracy in predicting mortality in critically ill dogs.

Main Methods:

• Retrospective analysis of 96 healthy and 61 critically ill dogs.
• Calculation of SII from complete blood count (CBC) parameters within 1 hour of presentation.
• Comparison of CBC parameters, SII, and APPLE score between ill and healthy dogs, and between survivors and non-survivors.
• Receiver operating characteristic (ROC) curve analysis to determine optimal SII cutoff for mortality prediction.

Main Results:

• Critically ill dogs had significantly higher median SII (1,997) than healthy controls (516).
• Non-survivors exhibited elevated white blood cell count, neutrophil count, SII, neutrophil-to-lymphocyte ratio (NLR), and APPLEfast score compared to survivors.
• SII demonstrated moderate accuracy in predicting mortality (AUC: 0.806), comparable to the APPLEfast score (AUC: 0.759).
• The 95% reference interval for SII in healthy dogs was 180-1,392.

Conclusions:

• The Systemic Immune-Inflammation Index (SII) is significantly increased in critically ill dogs.
• Elevated SII values are associated with an increased risk of mortality.
• SII is a valuable indicator for prognostic evaluation in canine critical care patients, warranting further validation.