Prognostic value of systemic immune-inflammation index and serological biomarkers for deep neck infections

Inflammatory biomarkers, including C-reactive protein, erythrocyte sedimentation rate, neutrophil to lymphocyte ratio, platelet to lymphocyte ratio, and the systemic immune-inflammation index, have been proposed as prognostic factors diverse pathologies. However, their application for deep neck infections has yet to be clarified.

We performed a retrospective study of 163 adult patients with diagnosis of deep neck infections with the aim to evaluate the association between serological biomarkers with complications and outcomes of patients with DNI. Studied variables included demographic data, complications of DNI, outcomes, complications and death of the included subjects. The evaluated serological biomarkers were hemoglobin, leukocytes, neutrophils, lymphocytes, platelets, glucose, creatinine, albumin, CRP, and ESR. NLR, PLR, and SIII index were estimated.

The patients' mean age was 40.6 ± 15.3 years. Complications of DNI were observed in 19.6% (n=32) patients, being the need for tracheostomy due to airway obstruction (11%, n=18) and mediastinitis (8.6%, n= 14) the most common. Evaluated subjects had an increased value of serological biomarkers (SII index 2639.9 ± 2062.9, NLR 11.3 ± 8.5, PLR 184.1 ± 108.5, CRP 12.6 ± 8.9 mg/dL, ESR 20.7 ± 9.1 mm/h). Patients with complications had a significantly higher value of all inflammatory parameters (p < 0.05). A SII index cut-off value of 2975 was selected from a ROC curve analysis. A sensitivity of 93.8%, specificity of 86.3%, a positive predictive value of 62.5%, and a negative predictive value of 98.3% are reported. The SII index was found to have an increased positive predictive value compared to NLR, PLR, and CRP for DNI complications.

Our analysis concluded that the SII index, NLR, and PLR are valuable biomarkers to assess the risk of complications from DNI. SII index showed a high accuracy for prediction of DNI complications with a cut-off value of 2975.