[A case-control study on the relationship between the ratio of neutrophils to lymphocytes in malignant tumors and ventilator-associated pneumonia].

OBJECTIVE

To explore the relationship between ventilator-associated pneumonia (VAP) and neutrophil/lymphocyte ratio (NLR) before mechanical ventilation in patients with malignant tumors.

METHODS

A retrospective nested case-control study was conducted. Patients with malignant tumor treated by mechanical ventilation admitted to the Third Affiliated Hospital of Guizhou Medical University from February 2015 to February 2020 were enrolled. The patients with VAP were selected as the case group, and the matched non-VAP cases were selected according to 1:2 as the control group. The clinical data were collected, and the differences of each index between the two groups were compared. The influencing factors of VAP in patients with malignant tumor were analyzed by multivariate Logistic regression.

RESULTS

During the study period, 1 271 patients with malignant tumors were treated with mechanical ventilation, of which 241 cases had VAP, and the incidence of VAP was 18.96%. There were 232 VAP patients in the case group matched 464 non-VAP patients in the control group. The clinical data of age, gender, hospitalization diagnosis, primary tumor, regional lymph node and distant metastasis (TNM) stage, acute physiology and chronic health evaluation II (APACHE II), complications, duration of mechanical ventilation, hemoglobin (Hb) and serum albumin (Alb) levels were balanced and comparable between the two groups, and the cluster nursing measures were consistent. Compared with the control group, although there was no significant difference in neutrophil count (NEU) and lymphocyte count (LYM) in the case group [NEU (×10/L): 3.81±1.07 vs. 3.64±1.05, LYM (×10/L): 2.06±0.59 vs. 2.15±0.62, both P > 0.05], NLR was significantly increased (2.07±1.05 vs. 1.89±0.96, P < 0.05), and the hospital stay was significantly longer (days: 24.84±3.81 vs. 13.19±3.98, P < 0.01). NLR, gender, age, APACHE II score, TNM stage, Hb, serum Alb and duration of mechanical ventilation were included in multivariate Logistic regression analysis. The results showed that patients with elevated NLR had higher risk of VAP [odds ratio (OR) = 1.187, 95% confidence interval (95%CI) was 1.015-1.387, P = 0.032]. In patients with VAP, NLR was negatively correlated with the time of mechanical ventilation before VAP (r = -0.327, P = 0.000), and positively correlated with the time of treatment with antibiotics after VAP (r = 0.559, P = 0.000).

CONCLUSIONS

Elevated NLR in patients with malignant tumors who were on mechanical ventilation can significantly increase the risk of VAP and increase the difficulty of treatment.