The Significance of Systemic Immune-Inflammatory Index and Platelet-Neutrophil Ratio on Early Mortality in Septic Shock Patients and their Association with Vitamin D and Parathyroid Hormone Ratio

Objectives: Sepsis is a life-threatening organ dysfunction characterized by complex pro-inflammatory and anti-inflammatory processes. Vitamin D deficiency is frequently observed in sepsis and associated with worse outcomes. We aimed to evaluate the effect of vitamin D-to-PTH ratio, systemic immune-inflammatory index (SII), and platelet-to-neutrophil ratio (PNR) on mortality in septic shock patients with vitamin D deficiency and insufficiency.
Material and methods: In this cross-sectional study, vitamin D insufficiency was defined as vitamin D levels between 12-20 ng/ml and vitamin D deficiency as < 12 ng/ml. The SII is calculated by multiplying the neutrophil count with the platelet count and dividing the result by the lymphocyte count (N*P/L), and the PNR is calculated by dividing the platelet count by the neutrophil count (P/N). We used receiver operating curve (ROC) analysis, logistic regression analysis, and Kaplan-Meier survival analysis to determine the association between SII, PNR, vitamin D deficiency, vitamin D-to-PTH ratio and early mortality within 7-days.
Results: This study consisted of 39 patients with septic shock. While 11(28%) of patients had vitamin D insufficiency, 28(72%) had vitamin D deficiency. Vitamin D insufficiency was associated with higher levels of SII and PNR than vitamin D deficiency. ROC analysis showed that 0.077 and 67 are cut-off values with the highest sensitivity and specificity for the vitamin D-to-PTH ratio (AUC: 0.77, p=0.01) and SII (AUC: 0.78, p=0.008) to predict early mortality. Both cut-off values were significantly associated with mortality in logistic regression analysis. SII higher than 67 and vitamin D-to-PTH ratio higher than 0.077 were associated with survival in 7-days (91% vs. 60%, p=0.004, and 91% vs. 63%, p=0.006, respectively).
Conclusion: SII was significantly suppressed in patients with vitamin D deficiency which was associated with increased mortality in septic shock. In addition, the decreased level of vitamin D-to-PTH ratio, which could be an indicator of immune balance, may be associated with early mortality in the intensive care unit.