Research On The Application Value Of Metagenomic Next-generation Sequencing In Diagnosing Unexplained Pulmonary Infection

Research Background:Pulmonary infection is one of the most common infectious diseases in the clinic.It is a lung inflammation caused by various pathogenic microorganisms.It has a high morbidity and mortality.Due to the rapid development of modern medicine,with the wide application of broad-spectrum antibacterial drugs,glucocorticoids,immunosupp-ressive agents,etc.,the probability of various atypical pathogen infections,broadspectrum drug-resistant pathogen infections,and mixed infections of multiple pathogens is increasing,It puts forward higher requirements for the rapid and accurate detection of etiology.The traditional clinical detection methods are mostly sputum and bronchoalveolar lavage fluid(BALF)pathogen isolation,culture and identification,but the detection time is longer and the positive rate is low.Molecular diagnostic methods can quickly detect pathogens,but are prone to false positive results,and cannot detect new pathogen infections,multi-drug pathogen infections,and mixed infections.Metagenomic next generation sequencing(mNGS)technology as a new type of pathogenic detection method,due to its advantages of high throughput,low cost,high sensitivity,unbiased,etc.,in the detection of infectious disease etiology The value of this aspect is becoming increasingly apparent.Purpose:(1)Compare the effectiveness of mNGS technology and traditional laboratory testing methods in the etiological diagnosis of lung infections of unknown etiology;(2)Explore the potential application value of mNGS in the etiological diagnosis of lung infections.Methods:A retrospective analysis of 56 inpatients diagnosed with pulmonary infection and mNGS testing in the respiratory ward and respiratory intensive care unit of the First Affiliated Hospital of Nanchang University from January 2018 to December 2019.Collect basic information,medical history,physical signs,laboratory and other auxiliary examination results of all patients.In the routine diagnosis and treatment,the patient’s sputum,BALF,blood,pleural effusion or lung tissue and other specimens are collected and sent to the general laboratory for etiological testing(eg sputum smear,sputum culture,BALF culture,blood culture,nucleic acid detection),Antigen and antibody detection,etc.)and mNGS detection,based on the patient’s clinical characteristics and related auxiliary examination results,form a final etiological diagnosis.Use McNemar test to compare the difference between mNGS and traditional laboratory detection methods to diagnose lung infections,and compare the effectiveness of the two in bacterial,fungal,viral,atypical pathogens,and tuberculosis lung infections;master the common pulmonary infections in undergraduate departments Distribution of pathogens.Results:A total of 44 patients(27 males and 17 females,with an average age of 57.30years)of 43 pulmonary alveolar lavage fluid mNGS specimens and 10 venous blood mNGS specimens were included.mNGS detected 51 pathogens with a positive rate of84.09%;traditional laboratories detected 29 pathogens with a positive rate of 59.09%.Using McNemar test to compare the results of mNGS in 44 patients with unexplained lung infection and traditional laboratory tests,the difference between the two is statistically significant(p= 0.007 <0.05),it can be considered that the NGS test has a higher positive rate than traditional laboratory tests;But Kappa = 0.22 <0.4,it is considered that the consistency of the two detection methods is poor.The positive rate of mNGS in diagnosing viral infections and atypical pathogen infections is significantly higher than traditional methods,with P values ??of 0.041(84.62% vs38.46%)and <0.01(100.0% vs 14.29%);among patients with bacterial and fungal infections,The positive rate of mNGS is higher than the traditional method,but the difference is not obvious;3 patients with M.tuberculosis infection,because the sample size is too small to compare the difference between the two.All 11 cases of mixed infections were diagnosed by mNGS,of which only 2 cases were detected by traditional methods,and 2 cases had no pathogens detected by traditional methods.Inthis study,bacterial infections were dominated by Gram-negative bacteria,of which Pseudomonas aeruginosa,Klebsiella pneumoniae,and Acinetobacter baumannii were common;viral infections were mainly herpes virus,mainly human herpes Virus type1(herpes simplex virus type 1),human herpes virus type 4(EB virus),human herpes virus type 5(cytomegalovirus),most of the viruses are mixed with bacteria and fungi;fungal infection is Yersinia Pneumocystis is more common;the atypical pathogen is Chlamydia psittaci.Conclusions:The effectiveness of mNGS in the diagnosis of pulmonary infections is generally better than traditional methods,and it is more significant in the diagnosis of viruses,atypical pathogens and mixed infections.Although mNGS cannot replace the traditional method as the gold standard for the diagnosis of lung infections,it can be used as an effective supplementary method for clinical pathogenic detection.The combination of the two can increase the detection rate of pathogens caused by lung infections.