[Predictive value of neutrophil to lymphocyte ratio on 28-day mortality of patients with severe pneumonia].

Objective To evaluate the predictive value of neutrophil to lymphocyte ratio (NLR) on 28-day mortality of patients with severe pneumonia. Methods The clinical data of 214 severe pneumonia patients admitted to the department of emergency medicine of the First Affiliated Hospital of Xi'an Jiao Tong University from January 2015 to December 2018 were retrospectively analyzed. The clinical parameters, such as gender, age, underlying diseases, and blood routine, procalcitonin (PCT), liver and kidney function, blood lactic acid (Lac), arterial partial pressure of oxygen (PaO2) at admission or within 24 hours after admission were reviewed. NLR, oxygenation index (PaO2/FiO2) and acute physiology and chronic health evaluation Ⅱ (APACHEⅡ) were calculated, and the change tendency of each index within 3 days after admission were observed. The patients were divided into survival group and death group according to 28-day outcomes. Multivariate Logistic regression analysis was used to screen the high risk factors of 28-day mortality in patients with severe pneumonia. Receiver operating characteristic (ROC) curve was drawn to evaluate the predictive value of NLR for 28-day mortality risk in patients with severe pneumonia. Results 214 patients were enrolled in the analysis, 132 survived in 28 days and 82 died. Compared with survival group, the white blood cell (WBC), neutrophil (NEU), NLR, PCT, Lac and APACHEⅡ scores were significantly increased, and lymphocyte (LYM) was significantly decreased in the death group. There was no significant difference in gender, age, basic diseases, platelet count (PLT), liver and kidney function parameters, or PaO2/FiO2 between the two groups. The NLR, PCT, Lac and APACHEⅡ score in the death group were increased gradually within 3 days after admission, PaO2/FiO2 was decreased gradually, which showed significant differences as compared with survival group at 3 days after admission [NLR: 27.15±7.61 vs. 14.66±4.83, PCT (μg/L): 13.52±3.22 vs. 6.41±4.22, Lac (mmol/L): 6.78±1.70 vs. 2.74±1.15, APACHEⅡ score: 37.76±5.30 vs. 22.11±4.94, PaO2/FiO2 (mmHg, 1 mmHg = 0.133 kPa): 114.12±20.16 vs. 186.49±13.95, all P < 0.05]. Multiple Logistic regression analysis showed that NLR [odds ratio (OR) = 1.163, 95% confidence interval (95%CI) = 1.007-1.343, P = 0.040], PCT (OR = 1.210, 95%CI = 1.098-1.333, P = 0.001), Lac (OR = 1.263, 95%CI = 1.011-1.579, P = 0.040) and APACHEⅡ score (OR = 1.103, 95%CI = 1.032-1.179, P = 0.004) were the independent risk factors of 28-day mortality in the patients with severe pneumonia. ROC curve analysis showed that compared with the traditional indicators including PCT, Lac, and APACHEⅡ score, NLR showed a good predictive value for 28-day mortality in the patients with severe pneumonia [area under ROC curve (AUC): 0.791 vs. 0.707, 0.690, 0.720]. When the optimal cut-off value of NLR was 14.92, the sensitivity was 71.95% and the specificity was 73.48%, meanwhile, the positive likelihood ratio was 2.713 and the negative likelihood ratio was 0.382. Conclusion The increased NLR at admission is a high risk factor of 28-day mortality in patients with severe pneumonia, which is useful for predicting prognosis of patients with severe pneumonia. Key words: Severe pneumonia; Neutrophil to lymphocyte ratio; Predictive value; Mortality