Application Scenarios and Value Boundaries of Pathogen Nucleic Acid Testing in the Diagnosis and Treatment of Infectious Diseases

Why is pathogen nucleic acid testing needed in clinical practice?

The precision diagnosis and treatment of infectious diseases depend on etiological evidence. Traditional culture methods have a long turnaround time, and the positive rate of culture for some fastidious bacteria, viruses, or samples after antimicrobial use is limited. Pathogen nucleic acid testing, by identifying microorganism-specific nucleic acid fragments, can provide etiological clues within a relatively short time and offer a reference for the initial selection or adjustment of anti-infective regimens. This is especially valuable in the differential diagnosis of severe infections, infections in immunocompromised populations, and fever of unknown origin, where the timeliness and sensitivity of nucleic acid testing have clinical value.

Application in respiratory tract infections

There are many types of respiratory pathogens with a high degree of symptom overlap. Multiplex nucleic acid testing can simultaneously cover common targets such as influenza virus, respiratory syncytial virus, adenovirus, parainfluenza virus, Mycoplasma pneumoniae, and Chlamydia pneumoniae. For hospitalized patients, elderly patients, or individuals with multiple underlying diseases, early identification of the pathogen helps reduce unnecessary empirical antimicrobial use. However, microorganisms in respiratory samples may represent colonization rather than causation, and positive results need to be interpreted comprehensively in combination with load, clinical manifestations, and imaging features.

Bloodstream infection and sepsis-related testing

Bloodstream infections have an acute onset and rapid progression. Blood culture remains an important reference for diagnosis, but its positive rate is affected by the timing of blood collection, blood volume, and antimicrobial use. Pathogen nucleic acid testing can serve as a supplementary method by directly detecting cell-free pathogen nucleic acids in plasma or whole blood. Some testing protocols can also cover drug resistance genes, providing a molecular-level reference for the clinical selection of antimicrobial agents. It should be noted that nucleic acid testing cannot completely replace blood culture, and antimicrobial susceptibility testing of isolated strains remains an important basis for the refined adjustment of antimicrobial agents.

Auxiliary diagnosis of central nervous system infections

Cerebrospinal fluid pathogen nucleic acid testing is helpful for the early identification of diseases such as viral encephalitis and tuberculous meningitis. Herpes simplex virus, enterovirus, and varicella-zoster virus are common testing targets. For bacterial meningitis, cerebrospinal fluid culture and smear remain fundamental, and nucleic acid testing can provide supplementary information when culture is negative but clinical suspicion is high. Laboratories should clarify the detection limit and specificity of the testing method to avoid false positives caused by trace nucleic acid contamination that may mislead treatment.

Public health surveillance and outbreak response

In infectious disease surveillance and the management of clustered outbreaks, pathogen nucleic acid testing plays a role in rapid screening, genotyping, and traceability analysis. High-throughput automated extraction and amplification systems have improved the capacity for large-scale sample processing. Primary-level institutions can use relatively simple-to-operate isothermal amplification equipment for initial screening, and positive samples can then be sent to regional central laboratories for confirmation or sequencing. In surveillance systems, sampling standards, testing targets, and result reporting criteria should be unified to ensure comparability of data across different laboratories.

Boundaries of result interpretation and communication

A positive pathogen nucleic acid test indicates the presence of the target nucleic acid, but it does not necessarily equate to active infection. Convalescent patients may continue to shed nucleic acid fragments, and multiple targets may be positive in immunocompromised or mixed infection scenarios. Negative results are affected by sampling quality, pathogen load, nucleic acid degradation, and the coverage of testing targets, and cannot completely rule out infection. When interpreting reports, clinicians should pay attention to specimen type, testing method, and laboratory remarks. Establishing routine communication mechanisms between the clinical laboratory and clinical departments helps reduce misinterpretation and improve the clinical translation efficiency of test results.