Editor's Note: Patients with hematological disorders are often immunocompromised due to their primary disease or treatment, making them susceptible to infections. These infections often present atypically and can be caused by a wide variety of pathogens. Traditional diagnostic methods have low positivity rates and are time-consuming. Pathogen diagnosis is crucial for optimizing anti-infection treatment and improving patient outcomes. Metagenomic Next-Generation Sequencing (mNGS) is a high-throughput, broad-coverage diagnostic technique that has been widely applied in clinical infection settings. In diagnosing infections in hematological patients, mNGS offers high positivity rates, minimal interference from antimicrobial drugs, and broad pathogen coverage. To standardize the application of mNGS in hematological patients and optimize report interpretation, the Infectious Diseases Group of the Chinese Society of Hematology has invited experts in the field to develop a consensus.At the recent Fourth National Conference on Bacterial and Fungal Infections (BISC 2024) organized by the Chinese Medical Association, Professor Sizhou Feng from the Institute of Hematology, Chinese Academy of Medical Sciences, delivered an insightful interpretation of this consensus and shared updates on the clinical application of mNGS.
- Diagnostic Advantages of Pathogen mNGS
A study showed that in patients with neutropenia, the positivity rate of traditional microbiological tests was only 25.5%, whereas it significantly increased to 73.4% with mNGS testing of blood samples. The detection rates were 42.4% for bacteria, 21.1% for fungi, and 47.0% for viruses, demonstrating the technology’s broad coverage of various pathogens. Notably, mNGS showed a significant advantage in detecting fungi, providing robust support for clinical diagnosis and treatment.
Moreover, the study indicated that for bloodstream infections (BSI), mNGS could detect pathogens earlier than the occurrence of BSI; if symptoms persist after BSI treatment and blood cultures turn negative, mNGS can still detect pathogens.
- Clinical mNGS Indications for Infections in Hematology Patients
Consensus 1:
Infections are common complications in patients with hematological diseases. When a suspected infection occurs, traditional microbiological tests should be the first choice, and pathogen mNGS should only be considered in special situations such as severe infections or suspected central nervous system infections.
Consensus 2:
For low-risk patients without a clear infection focus, if empirical antimicrobial treatment ≥7 days shows no significant improvement, consider sending peripheral blood samples for mNGS along with blood cultures. For high-risk patients, if initial empirical treatment fails within 72-96 hours, it is recommended to conduct traditional microbiological tests and blood mNGS simultaneously.
Consensus 3:
For patients suspected of BSI, collect blood culture samples and plasma samples simultaneously, storing the latter at -80°C. If blood cultures are negative within 72 hours and there is no improvement with anti-infection treatment, it is recommended to perform mNGS on the stored samples. For severe sepsis cases, it is advised to conduct both blood cultures and blood mNGS.
Consensus 4:
For lower respiratory tract infections, bronchoalveolar lavage fluid (BALF) is the preferred sample for traditional microbiological tests. For patients unable to undergo bronchoalveolar lavage, deep sputum samples can be collected and stored. If anti-infection treatment ≥72 hours does not improve symptoms or imaging shows worsening conditions, it is recommended to perform mNGS on stored samples. For severe lower respiratory tract infections or patients at high risk of rapid progression to severe conditions, both traditional microbiological tests and mNGS should be conducted simultaneously.
Consensus 5:
For suspected CNS infections, it is recommended to send cerebrospinal fluid for traditional microbiological tests and mNGS simultaneously, opting for DNA testing first and completing RNA testing if RNA viruses are considered.
This comprehensive approach in applying mNGS allows for more effective diagnosis and treatment optimization in hematological patients, enhancing patient outcomes while balancing the high costs and specific indications for this advanced diagnostic tool.
