April 29, 2026

mNGS Testing Workflow: Cost, Turnaround, and Results

Should Your Lab Use mNGS Testing?

For a clinical or research lab, the practical mNGS question is not only “what is metagenomic sequencing?” The decision is whether mNGS can return a useful pathogen answer fast enough, at a sequencing depth and sample cost your workflow can support.

The Micronbrane PaRTI-Seq™ workflow is designed around that decision point:

Turnaround: sample-to-report workflow in under 24 hours when host depletion, library prep, sequencing, and analysis are run as an integrated process.
Sequencing depth: approximately 5 million reads can support pathogen identification when host depletion is applied upstream, instead of the tens of millions of reads often required without depletion.
Cost model: PaRTI-Seq workflow modeling on an Illumina MiniSeq estimates $537.28 per sample with PaRTI-Seq versus $1,729.11 without PaRTI-Seq.
Clinical evidence: in a 45-patient sepsis evaluation, PaRTI-Seq reached a 74.4% pathogen-positive rate and 81.8% sensitivity against the post-antibiotic blood-culture reference.
Host-depletion evidence: an independent sepsis-sample study detected expected pathogens in 100% (8/8) of filtered gDNA mNGS samples and increased microbial reads from 925 to 9,351 RPM on average.

For labs evaluating mNGS, this makes host depletion and workflow design central. A generic “sequence everything” approach can rank for the definition of mNGS, but it does not answer the buyer question: whether the workflow can turn a low-biomass, host-rich specimen into an actionable report.

Looking for an mNGS product code? If your search is for a specific Micronbrane workflow component, start with the Products overview, Devin Host Depletion Filter, Unison Ultralow DNA Library Prep Kit, or PaRTI-Seq Analysis. Product-code queries such as `mngs-051` usually need a product, protocol, or ordering path rather than another definition of mNGS.

What mNGS Testing Does

mNGS testing — metagenomic next-generation sequencing — identifies pathogens directly from a clinical specimen by sequencing all nucleic acids in the sample. Unlike blood culture, which grows only organisms that can be cultured in vitro over two to five days, or targeted PCR, which detects only the specific organisms an assay was designed to find, mNGS can identify bacteria, fungi, viruses, and parasites in a single workflow. If the pathogen’s genome is in the sample, mNGS can detect it.

This unbiased approach carries a distinct set of clinical advantages: high diagnostic yield, detection of known and novel microbes without prior culture or hypothesis, faster turnaround than conventional diagnostics, and comprehensive genomic information that can guide antimicrobial selection. For cases where conventional diagnostics have failed — culture-negative sepsis, encephalitis of unknown etiology, pneumonia in an immunocompromised patient — mNGS provides a diagnostic path that targeted methods cannot. For a deeper look at how mNGS addresses the gap in culture-independent pathogen detection, and why the infectious disease diagnostic gap persists despite advances in targeted testing, see those linked articles.

How the mNGS Workflow Works (Sample to Report)

The mNGS workflow moves through six stages, from sample collection to an actionable pathogen report. One commercially validated implementation — the Micronbrane PaRTI-Seq™ workflow — completes this sequence in under 24 hours:

Stage 1 — Sample collection: the clinical specimen is collected and prepared for host-depletion processing.
Stage 2 — Host depletion by filtration: host-cell removal takes less than 5 minutes.
Stage 3 — Microbial DNA enrichment: microbial DNA enrichment takes approximately 1.5 hours.
Stage 4 — NGS library preparation: library construction takes approximately 2.5 hours.
Stage 5 — Sequencing: sequencing takes approximately 16 hours.
Stage 6 — Bioinformatics analysis and report: automated analysis and report generation takes approximately 0.5 hours per sample.

The bioinformatics stage in this PaRTI-Seq workflow applies automated quality checks, host genome read removal, background noise thresholds, and maps sequencing reads against a database of over 1,400 microorganisms. The depth required for accurate pathogen identification falls to approximately five million reads when host depletion is applied upstream — far below the tens of millions of reads that workflows without depletion require. For a detailed look at bioinformatics requirements, see mNGS bioinformatics analysis.

Why Host Interference Is the Central Barrier

In any clinical specimen, human DNA vastly outnumbers microbial DNA. Host reads can exceed 95% of all reads in many mNGS libraries — meaning that for every 100 sequencing reads, fewer than five carry information about pathogens. When a library is dominated by human sequence, the sequencer spends the majority of its capacity generating data that will be discarded before any pathogen analysis begins.

Removing host reads computationally after sequencing is possible, but it introduces its own costs. It requires substantial computational resources, risks discarding microbial reads that map partially to the human reference genome, and forces the workflow to sequence at substantially higher depth to achieve reliable coverage of low-abundance organisms. Reducing host DNA before sequencing — rather than after — is the more efficient path, and it opens the door to smaller, lower-cost sequencing platforms that cannot practically sequence at the depth that computational depletion demands.

The Devin Host Depletion Filter addresses this barrier by physically removing nucleated host cells from the sample before DNA extraction, using a zwitterionic membrane coating (ZISC technology) that selectively retains leukocytes regardless of membrane pore size. Validation testing demonstrated >99% white blood cell removal at input volumes from 3 mL to 13 mL, with microbial passing efficiency exceeding 90% for bacteria and viruses tested. The filter increases microbial pathogen DNA in human blood samples 10- to 1,000-fold. For a head-to-head comparison of depletion approaches and their impact on sequencing results, see how host depletion approaches compare and the associated host depletion whitepaper.

Clinical Evidence: mNGS vs Blood Culture in Sepsis

The strongest published evidence for mNGS in clinical infectious disease comes from a prospective study at Taipei Veterans General Hospital (TVGH). The study evaluated the PaRTI-Seq workflow — combining the Devin Host Depletion Filter and Microbial DNA Enrichment Kit — against standard blood culture for pathogen identification in septic patients. Fifty patients were enrolled, with complete results available for 45. Each patient provided samples for two serial blood cultures (BC1 collected on admission, BC2 collected on consent) and two mNGS runs: one using the full PaRTI-Seq host depletion workflow and one without depletion. (Chen YC et al., Molecular Diagnosis & Therapy 2025; DOI 10.1007/s40291-025-00797-3)

Positive pathogen identification rates across all four approaches:

PaRTI-Seq (mNGS with host depletion): 74.4% positive identification rate.
mNGS without host depletion: 51.1% positive identification rate.
First blood culture (BC1): 50.0% positive identification rate.
Second blood culture (BC2): 22.0% positive identification rate.

Using BC2 as the reference standard, PaRTI-Seq achieved 81.8% sensitivity compared with 63.6% for mNGS without filtration. Host depletion increased microbial read density from 46 to 243 reads per million QC reads, with an R² of 0.96 between filtered and unfiltered samples confirming that the filtration step did not alter the underlying microbial community composition. Complete results were available within 24 hours of sample collection — substantially faster than the 48- to 120-hour turnaround typical for blood culture. For a detailed summary of the study design and full results, see the TVGH sepsis mNGS study page or watch the corresponding TVGH webinar.

Sample Types mNGS Can Analyze

The Devin filter has been validated across a broad range of clinical specimen types: whole blood, plasma, cerebrospinal fluid (CSF), bronchoalveolar lavage (BAL), vitreous humor, synovial fluid, and other body fluids. Each specimen type presents a different host-to-pathogen ratio and a different starting DNA concentration, which directly affects which library preparation approach is appropriate.

Host-depleted specimens — particularly plasma and CSF — often contain DNA concentrations that fall below the detection limit of standard Qubit fluorometric assays (below 0.1 ng/µL). Standard library construction protocols that require 200 ng or more of input DNA cannot be applied to these samples. For these low-input specimens, the Unison Low-Input Library Preparation Kit is engineered for sub-nanogram inputs — bridging the gap that standard protocols cannot. The choice of library preparation kit is therefore as consequential as the choice of sequencing platform for host-depleted clinical specimens. The posts cfDNA vs gDNA assay design and mNGS without host interference explore these tradeoffs in detail for sepsis and sterile-site applications.

Key Limitations and How They Are Being Solved

Five limitations currently constrain routine clinical deployment of mNGS. Each has an active solution path.

Contamination. Reagents used in DNA extraction and library preparation carry background microbial DNA that can appear in sequencing results and be misattributed to the patient sample. Stringent reagent selection, spike-in controls, and background subtraction are required. The evidence base for how reagent contamination distorts mNGS results is well-documented in the literature.

Host interference. The dominant limiting factor for sensitivity and cost; addressed by physical host depletion before DNA extraction, as described in the section above.

Process complexity. A six-step workflow spanning specialized extraction instruments, a sequencer, and a bioinformatics platform creates infrastructure and training requirements that restrict routine mNGS to reference laboratories. Integration of standardized kits and automated pipelines is progressively reducing this barrier.

Sequencing costs. Per-sample sequencing cost remains the primary obstacle to routine clinical deployment. Effective host depletion reduces the sequencing depth required; multiplexing more samples per run lowers per-sample cost. The post on reducing mNGS costs covers the specific levers available. For platform-specific cost comparisons see short-read platforms for mNGS and the protocol for long-read PCR amplification on lower-cost nanopore instruments.

Bioinformatic pipelines. Interpreting metagenomic output requires curated reference databases, contamination filters, and clinically meaningful pathogen-significance thresholds that most clinical microbiology labs do not maintain. Automated, cloud-based pipelines with pre-configured databases are the current solution — making bioinformatics expertise optional at the ordering institution.

When to Use mNGS (Decision Framework)

mNGS is not a first-line replacement for blood culture in every sepsis case. It is most valuable as a second-line diagnostic — and increasingly as a first-line option — for clinical scenarios where conventional diagnostics are unlikely to yield a result quickly enough to guide treatment. The TVGH study identified positive cases via PaRTI-Seq where the second blood culture returned negative, including Pseudomonas aeruginosa and Achromobacter species that standard culture failed to capture by the second draw. For a method-by-method decision guide with the head-to-head yield, turnaround, and cost-per-result data, see Traditional Culture vs mNGS: A Data-Driven Comparison.

Consider mNGS when any of the following apply:

Culture is negative after 48 hours in a patient with active sepsis or severe infection. mNGS provides a diagnostic path when the organism will not grow in standard media or has been suppressed by prior antibiotics.
The patient is immunocompromised. Unusual opportunistic pathogens — fungal species, atypical bacteria, reactivated herpesviruses — are plausible and targeted PCR panels would need to include dozens of assays to span the same breadth.
A novel or emerging pathogen is suspected, such as in outbreak investigation or travel-associated illness, where no targeted assay exists or the causative agent is not yet identified.
Prior targeted testing has not explained the clinical picture, particularly in culture-negative endocarditis, encephalitis, febrile neutropenia, or post-transplant infections.

The 24-hour turnaround demonstrated in the TVGH study is achievable when a validated host-depletion workflow and automated bioinformatics pipeline are in place. In epidemiological contexts — outbreak surveillance, infection control monitoring, public health response — the same approach suits settings that require versatile, broad-spectrum pathogen detection without extensive reagent inventories or institutional laboratory infrastructure.

mNGS Testing FAQs

What is mNGS testing?

mNGS testing is a broad pathogen-identification method that sequences all nucleic acids in a sample and compares the reads against microbial reference databases. Unlike culture or single-target PCR, mNGS does not require the lab to choose one organism before testing. That makes it useful when the suspected infection is culture-negative, polymicrobial, unusual, or outside a standard diagnostic panel.

When should a lab consider mNGS testing?

A lab should consider mNGS when conventional diagnostics are unlikely to answer the clinical question quickly enough: culture-negative sepsis, central nervous system infection, suspected polymicrobial infection, immunocompromised patients, outbreak investigation, or cases where targeted PCR panels would need to cover too many organisms. The strongest results come from pairing sequencing with host depletion, contamination controls, and a validated analysis pipeline.

How long does mNGS testing take?

Turnaround depends on the workflow. In the PaRTI-Seq workflow, host depletion takes less than 5 minutes, microbial DNA enrichment takes about 1.5 hours, library construction takes about 2.5 hours, sequencing takes about 16 hours, and automated analysis takes about 0.5 hours per sample. That supports a sample-to-report workflow in under 24 hours.

How much does mNGS testing cost?

The cost depends heavily on host depletion and sequencing depth. PaRTI-Seq value modeling on an Illumina MiniSeq estimates $537.28 per sample with host depletion and integrated analysis versus $1,729.11 without PaRTI-Seq. The difference comes from reducing host background, lowering required read depth, and improving sample multiplexing.

How is mNGS different from targeted PCR?

Targeted PCR asks whether a specific organism or gene is present. mNGS asks what microbial nucleic acids are present in the sample. PCR is faster and simpler when the target is known; mNGS is more useful when the causative organism is unknown, unexpected, or mixed with other organisms. In low-biomass samples, host depletion and contamination QC are critical because the microbial signal may otherwise be too small to interpret.

Ready to evaluate mNGS for your setting? Start with the Devin Host Depletion Filter for sample preparation, Unison Library Preparation Kits for low-input sequencing libraries, and PaRTI-Seq Analysis for pathogen reporting.