Relationship between systemic immune inflammation index and amputation in patients with diabetic foot ulcer

The systemic immune inflammation index (SII) is a cost-effective biomarker calculated by lymphocyte, neutrophil and platelet counts and is currently being studied in various diseases. Since there is no study examining the relationship between SII and diabetic foot ulcers (DFU) in the literature, our aim was to investigate the relationship between SII and amputation rate in DFU. Type 2 DM 511 patients with DFU were screened from 2017 to 2021. Laboratory data obtained on the first day of hospitalization were considered. Platelet-to-lymphocyte ratio (PLR), neutrophil-to-lymphocyte ratio (NLR) and SII were calculated from routine blood count. Participants were divided into two groups as amputation (Group 1) and non-amputation (Group 2). Amputation rate was 18.8%. The A1c (8.80 (3.26) % vs. 9.52 (3.10) %, p = 0.007) and HGB (10.17 ± 2.16 g/dL vs. 12.05 ± 2.20 g/dL, p < 0.001) levels, and lymphocyte count (1.81 (1.16) vs. 2.05 (1.11), p = 0.015) were significantly lower in Group 1 than Group 2. The counts of WBC (14.01 (9.16) × 109/L vs. 10.41 (5.82) × 109/L), PLT (393.35 (196.98) × 109/L vs. 312.05 (141.33) × 109/L), neutrophil (11.52 (8.75) × 109/L vs. 6.93 (5.96) × 109/L), PLR (226.04 (159.24) × 109/L vs. 153.12 (101.91) × 109/L), NLR (6.64 (6.93) vs. 3.34 (3.99)) and SII (2505.86 (3957.47) × 109/L vs. 1092.50 (1476.08) × 109/L), and the levels of CRP (14.12 (12.66) mg/dL vs. 3.86 (12.63) mg/dL) and ESR (87.50 (50.50) mm/h vs. 63.00 (57.25) mm/h) were significantly higher in Group 1 than Group 2 (all p < 0.001). AUC of ROC analysis of PLR was 0.666 (95% CI, 0.604–0.728), NLR was 0.695 (95% CI, 0.638–0.752) and SII was 0.716 (95% CI, 0.661–0.772) for the predicting of amputation and the SII had the best AUC with 67.4% sensitivity and 63.3%specificty. SII is a cost-effective and readily available marker, but alone may not be sufficient to predict the risk of amputation in DFU. In our results, the predictive role of SII alone or with other markers for future DFU and its role in predicting other chronic diabetic complications will be evaluated in extensive studies.