Prognostic value of IL-6/lymphocyte ratio to predict mortality in severe pneumonia in an intensive care unit of a northeast hospital in Mexico

Inflammatory response is an important factor to pathogenesis of infectious diseases, making the identification of biomarkers crucial(1). IL-6/lymphocyte ratio has been used as an independent risk factor for mortality due to COVID- 19(2). Aim to determine IL-6/lymphocyte ratio as prognostic tool for mortality in severe pneumonia. Retrospective cohort of adult patient records with severe pneumonia (COVID-19) during March 2020 to January 2021, admitted in the intensive care unit (ICU) during first 24 h. We obtained clinical, laboratory data, ventilatory support and vasopressor use, mechanical ventilation (MV) days, hospital and ICU length of stay (LOS). For numerical variables mean, median, standard deviation (SD), interquartile range (IQR) and for categorical variables percentages. An area under the curve receiver operating characteristic (AUC ROC) calculated the value with higher sensitivity. Specificity, predictive values (PPV/NPV), likelihood ratios (LR) and odds ratio (OR) for mortality were obtained. We included 99 adult patient records with diagnosis of severe pneumonia in ICU. 81.8% were male, mean age was 46 years, mean BMI was 27.3 kg/m2. Most common comorbidities were hypertension (63.6%) and T2DM (45.5%). APACHE II 10.8 (SD ±19.8), SOFA 7 (SD ± 6.8). Laboratory data included leukocytes 1.43 10 × 9/L (SD ±5093) lymphocytes 0.71 10 × 9/L (SD ± 0.302) haemoglobin 12.7 g/dl (SD ±2), creatinine 2.5 mg/dl (SD ±4.6) albumin 3.9 g/L (SD ±0.73) D dimer 2355.6 ng/ml (SD ± 2815). Inflammatory markers; C-reactive protein 127.3 mg/L (SD ±113), interleukin-6 76.8 pg/ml (SD ± 107), IL-6/lymphocyte ratio median 24.5 (IQR18.8–86.6). Patients required MV 82.8%, vasopresor use 72.7% and steroid use 81.8%. While in ICU, ventilator associated penumonia (VAP) occurred in 45.5%. Use of MV lasted 8.8 days (SD ± 9.3), hospital LOS 22.9 days (SD ± 12.2), ICU LOS 17.5 days (SD ± 11.4). On day 28, 72.7% died. AUC ROC 0.458 (CI 95% 0.341–0.576, p = 0.52), sensitivity 75%, specificity 33.3%, PPV 75%, NPV 33.3%, LR+ 1.12, LR- 0.75, for a IL-6/lymphocyte ratio value of 20.12 (Fig. 1). OR IL6/L ratio > 20.1 and death 1.5 (CI 0.573–3.9, p = 0.68). IL-6/lymphocyte ratio had a lower diagnostic performance in comparision with SOFA and APACHE II scores for mortality prediction in patients with severe pneumonia. 1. Wafa Sayah, Ismahane Berkane, Imene Guermache, et al. Interleukin-6, procalcitonin and neutrophil-to-lymphocyte ratio: Potential immune-inflammatory parameters to identify s