Absolutely. mNGS (metagenomic next-generation sequencing) technology can simultaneously detect both DNA and RNA, which is one of its most significant advantages over traditional testing methods. This combination of testing for both DNA and RNA pathogens is often referred to as mNGS (for DNA pathogens) + RNA-Seq (for RNA pathogens), and in clinical practice, is often collectively referred to as "pathogen metagenomic sequencing."

The following explains its principles, advantages, and application scenarios in detail:

1. How to achieve DNA and RNA co-detection?

Co-detection is not simply a matter of throwing a sample into a machine; it requires a specific laboratory process:

Sample nucleic acid extraction: First, total nucleic acid (including both DNA and RNA) is extracted from clinical samples (such as blood, cerebrospinal fluid, and bronchoalveolar lavage fluid) using a specialized extraction kit.

Reverse transcription (key step): Reverse transcriptase is added to the extracted total nucleic acid to reverse-transcribe all RNA (both human and pathogenic) into complementary DNA (cDNA).

Sequencing Library Construction: At this point, all genetic material in the sample is converted to DNA (original DNA + cDNA reverse-transcribed from RNA). This DNA is then fragmented, adapter-added, and processed using a universal library construction kit to construct a library ready for sequencing.

High-Throughput Sequencing and Bioinformatics Analysis: After high-throughput sequencing of the library, the massive amount of data generated undergoes specialized bioinformatics pipelines:

Human Sequence Removal: Sequences belonging to the human genome are aligned and filtered out to reduce data volume and improve analytical sensitivity.

Taxonomic Comparison: The remaining sequences are compared against a vast database of pathogenic microorganisms (including bacteria, DNA viruses, RNA viruses, fungi, parasites, and more).

Report Generation: A report is generated, listing all suspected pathogens detected (including DNA and RNA viruses) and providing relevant read count information.

2. The Significant Advantages of DNA/RNA Co-Testing

Broad-spectrum & Hypothesis-free: Eliminating the need for pre-specified pathogens, a single test can screen for all potential pathogens in a sample, including unknown, rare, and emerging viruses (e.g., SARS-CoV-2 and novel Bunyaviruses, discovered through this technology).

Efficient and Comprehensive: A single test can cover nearly all pathogens, making it particularly suitable for rapid etiology diagnosis in critically ill, difficult-to-diagnose, mixed-infection, and immunosuppressed patients, avoiding the time-consuming, traditional "one-by-one" testing process.

Discovering Unexpected Pathogens: Pathogens not previously considered clinically can often be discovered, providing new diagnostic insights.

3. Main Application Scenarios

This technology is generally not the first-line choice, but plays a key role when traditional methods cannot clearly identify the cause:

Fever of Unknown Origin (FUO)

Intracranial infection of unknown origin (such as meningitis, encephalitis)

Pneumonia of unknown origin (especially in critically ill and immunocompromised patients)

Etiological diagnosis of septic shock

Diagnosis of opportunistic infections

4. Limitations

High Cost: Sequencing and data analysis are expensive.

High Technical Requirements: Requires extremely high laboratory hardware, operational procedures, and bioinformatics analysis capabilities.

Difficulty distinguishing between colonization and infection: Detecting a microbial sequence does not guarantee that it is the culprit; clinicians must make a comprehensive assessment based on the patient's symptoms, signs, and other test results.

Sensitivity Issues: Some samples with low pathogen loads may miss detection.

In summary, mNGS technology, through the key step of "reverse transcription," successfully enables the simultaneous detection of both DNA and RNA pathogens. It is a powerful and unbiased pathogen screening tool that plays an irreplaceable role in the diagnosis of difficult and critical infections and is an important advancement in modern medical diagnostic technology.