摘要下呼吸道感染的病原学诊断一直是临床难题，宏基因组二代测序（mNGS）的广泛应用为临床提供了一种快速、准确的病原学诊断方法。但mNGS检测结果究竟应该如何解读，特别是检测出低序列数病原体时到底有无诊断价值，一直困扰着临床医生。本文从下呼吸道感染mNGS检测出低序列数的定义、发生的原因、确定结果可靠性的方法和如何结合临床正确解读低序列数报告4个方面进行讨论，希望通过全面掌握检测知识来建立正确的临床分析思维，以提高下呼吸道感染mNGS检出低序列数病原体的诊断水平。

abstractsPathogenic diagnosis of lower respiratory tract infection has always been a clinical problem. The widespread application of metagenomic next-generation sequencing(mNGS)provides a rapid and accurate method for pathogenic diagnosis. However, how to interpret the results of mNGS detection, especially whether it has diagnostic value in detecting pathogens with low sequence number, has always puzzled clinicians. This paper discusses the definition of low sequence number (lower reads)detected by mNGS in lower respiratory tract infection, the cause of occurrence, the method to determine the reliability of the results, and how to correctly interpret the low sequence number report in combination with clinical practice. It is hoped that by comprehensively mastering the detection knowledge, the proper clinical analysis thinking can be established to improve the diagnostic ability of pathogens with low sequence number detected by mNGS in lower respiratory tract infection.