Role of the Systemic Immune-Inflammation Biomarkers (Systemic Immune-Inflammation Index [SII], Neutrophil-to-Lymphocyte Ratio [NLR], Platelet/Lymphocyte Ratio [PLR], Delta Neutrophil Index [DNI]) in Diagnosis and Complication Prediction of Geriatric Appendicitis.

BACKGROUND: Acute appendicitis (AA) is an emergency surgical condition with diagnostic difficulty and a high complication rate in geriatric patients due to atypical presentations. AIM: This study evaluated the diagnostic and prognostic value of the systemic immune-inflammation index (SII), delta neutrophil index (DNI), and neutrophil-to-lymphocyte ratio (NLR) in patients aged ≥65 years. METHODS: This retrospective study included 120 participants: 60 geriatric patients who underwent appendectomy for AA between January 2021 and October 2025 and 60 age-matched healthy controls. Demographic data, hematological parameters, and histopathological findings were analyzed. AA patients were classified as complicated or uncomplicated. Receiver operating characteristic (ROC) curve analysis was performed to assess diagnostic performance. RESULTS: White blood cell count (WBC), absolute neutrophil count, NLR, DNI, and SII were significantly higher in the AA group compared with controls (P < 0.05). Patients with complicated AA had higher absolute neutrophil count, NLR, platelet-to-lymphocyte ratio (PLR), DNI, C-reactive protein, and symptom duration than uncomplicated cases. ROC analysis showed 85% sensitivity for SII (cutoff 0.84) and NLR (cutoff 3.79) in diagnosing AA. For predicting complications, SII (cutoff 1.71) showed 77.3% sensitivity and 68.4% specificity, while DNI (cutoff 0.055) had the highest specificity (71.1%). CONCLUSION: Hematological-based indices such as SII, NLR, and DNI are inexpensive and easily accessible markers for diagnosing AA and predicting complications in geriatric patients, although their diagnostic performance differs between outcomes.