Retrospective analysis of clinical data from 50 hospital-admitted patients with suspected pulmonary infection (as judged by clinical manifestations and imaging findings) was performed on study participants who had collected two different samples of alveolar lavage fluid (BALF) and sputum and underwent metagenomic next generation sequencing (mNGS) and routine pathogen detection, respectively. The positive rate of pathogen detection and the consistency of pathogen detection results of the two detection methods were compared to evaluate the clinical manifestation and role of mNGS in pathogen diagnosis.

Pulmonary infection is a common type of respiratory infection that can lead to multiple complications and is considered the most important infectious disease worldwide due to its high morbidity and mortality. Lung infections, caused by one or more pathogens such as bacteria, viruses, fungi and parasites, are not easily distinguishable clinically and are among the top 10 causes of death worldwide. Therefore, early and accurate identification of the cause of infection for patients with pulmonary infection is of great significance for subsequent treatment and improvement of prognosis. At present, the main traditional diagnostic methods for pulmonary infection are microbial culture, antigen and antibody detection and PCR nucleic acid detection technology. Although microbial culture is the gold standard for microbial identification, it takes a long time to detect some viruses and parasites. The sensitivity of antigen and antibody detection is poor. PCR nucleic acid detection method has high sensitivity and specificity, but it can not detect all pathogens causing lung infection. Therefore, it is necessary to develop a fast, convenient and sensitive new detection technology to detect the pathogen of pulmonary infection. next generation sequencing (NGS) has the advantage of no assumptions and no dependence on culture, and can detect all pathogens in clinical samples without bias, and has been widely used in a variety of infectious diseases. This study collected the basic information of patients suspected of pulmonary infection in clinic, and conducted mNGS detection and routine pathogen detection on different samples of alveolar lavage fluid (BALF) and sputum, respectively, to evaluate the consistency of mNGS detection and routine detection and the positive pathogen detection rate, as well as the clinical application value of mNGS detection.

This study retrospectively analyzed 50 patients hospitalized in our hospital from January, 2019 to October, 2019, whose symptoms, signs, imaging and infection indicators met the diagnostic criteria for pulmonary infection, while routine etiological detection of sputum and pulmonary alveolar lavage fluid mNGS were performed.

Clinical data of relevant patients were collected, including gender, age, smoking status, clinical manifestations, length of stay before mNGS detection, antibiotic use before mNGS detection, imaging changes, laboratory examination and other basic information. Results were collected from study participants' alveolar lavage fluid (BALF), sputum for traditional pathogen tests (microbial culture and PCR nucleic acid detection techniques), and mNGS tests. The positive rate of pathogen detection and the consistency of detection results of the two detection methods were compared.

Inclusion Criteria:

Inclusion criteria: Patients meeting diagnostic criteria for pulmonary infection between January 1, 2020 and October 31, 2023. Patients with pulmonary infection were diagnosed with new or worsening focal or diffuse infiltrating lesions on chest CT accompanied by at least one of the following four pneumonic-related clinical manifestations: (1) Recent cough, sputum, or aggravation of existing respiratory symptoms with or without purulent sputum, chest pain, dyspnea, and hemoptysis; ② Heat, T≥38℃; ③ Signs of lung consolidation and/or smell and moist rales; ④ Peripheral blood white blood cell count > 10*109/L or < 4*109/L.

Exclusion criteria: ① The patient did not undergo bronchoscopy; Absence of clinical or laboratory data.

Patients whose symptoms, signs, imaging, and infection indicators met the diagnostic criteria for pulmonary infection while routine etiological detection of sputum and pulmonary alveolar lavage fluid mNGS were performed.