Background High incidence rate of lower respiratory tract infection, especially hospital acquired pneumonia, leads to heavy medical burdens every year. Early diagnosis is essential for the prevention and treatment of lower respiratory tract infection.
Objective To analyze the classification characteristics of bronchoalveolar lavage fluid cells in patients with pulmonary bacterial infection and the diagnostic value of neutrophil ratio in bronchoalveolar lavage fluid for lower respiratory tract bacterial infection.
Methods Totally 141 bronchoalveolar lavage fluid cell samples sent by the First Medical Center of Chinese PLA General Hospital from January 2018 to December 2020 were included. According to the final clinical diagnosis, they were divided into pulmonary bacterial infection group and non-bacterial infection group. The basic information, primary diseases, laboratory results, clinical diagnosis were also collected.
Results There were 109 cases in bacterial infection group and 32 cases in non-bacterial infection group. The bacterial infection group and the non-bacterial infection group had significant differences (all P＜0.05) in proportions of neutrophils (47.025.7, 86.1% vs 9.63.7, 26.1%), macrophages (51.0±17.3% vs 82.2±11.1%) and lymphocytes (4.12.0, 15.1% vs 5.73.8, 21.6%). The threshold of neutrophil ratio in bronchoalveolar lavage fluid for the diagnosis of pulmonary bacterial infection was 25%, with the sensitivity of 0.844, the specificity of 0.969, and the area under the ROC curve of 0.899.
Conclusion Neutrophil ratio in bronchoalveolar lavage fluid over 25% is a strong indicator of pulmonary bacterial infection. Patients' clinical symptoms, imaging characteristics and past medical history can be combined for further diagnosis.
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