ngs testing: choosing a provider by panel and validation rather than by price, and reading a report that states its own limits

Choosing a provider, and which ngs kits the quote rests on

1. Panel design against your genes of interest. A targeted panel sequences a defined gene set very deeply and cheaply, and it sees nothing outside that set. Check the panel's content against your genes and, importantly, against the specific regions within them, since coverage within a gene is rarely uniform.
2. Validation and the limit of detection. Ask what the laboratory validated, on what sample types, and at what lowest detectable variant fraction. A detection claim without a stated validation is a capability statement rather than a specification you can rely on.
3. Accreditation appropriate to the use. Research testing and testing that informs a clinical decision sit under different regimes, and in the United States clinical testing requires a laboratory operating under the clinical laboratory improvement regime. A research result cannot be repurposed for a clinical decision because it was technically good.
4. Sample type and input requirement. Fresh tissue, fixed tissue, blood and cell-free material each have different input requirements and different achievable quality. Declare the sample type at quoting, since fixed material in particular constrains what is possible.
5. Turnaround, repeat policy and failures. Establish the turnaround, what happens when a sample fails quality control, whether a repeat is included and whether you are charged. Sample failures are routine in this field and the policy matters.

Reading the report

A good report states the regions covered and the regions that failed coverage, the variants detected with their fractions, the limit of detection applied, and explicitly what the test does not cover. A report that lists findings without stating its own limits is incomplete, because absence of a finding is meaningless without knowing what could have been found.

Ask for the underlying data as well as the report. Re-analysis with an updated annotation is common and impossible without the aligned reads.

Where this hub stops

This page is about an organisation choosing a testing provider: panels, validation, accreditation and reports. It is not medical advice and does not interpret any individual result.

Where a result could inform a clinical decision, that interpretation belongs with a clinician and a laboratory operating under the appropriate clinical regime, not with a research testing provider or with this site.

An ngs laboratory, and what to ask of one

An NGS laboratory is judged on the parts a sequencing price does not cover: the accreditation it holds and for which assays, the sample types and the input amounts it accepts, the depth and coverage it guarantees rather than averages, the pipeline version and reference it calls against, and what it does with a failed library. Ask for a specimen report before the quote, because the report is the deliverable and the differences between laboratories show there. Turnaround should be quoted from sample receipt, not from the start of the run.

ngs service providers, and how to compare them

NGS service providers quote in different units, which is where most comparisons fail. Normalise everything to the deliverable: cost per sample at the depth you need, with library preparation, quality control, sequencing and the analysis you will actually use included, and the data delivery method named. Then read the terms that do not appear in the price, minimum batch sizes, the re-run policy when coverage falls short, data retention and who owns the raw files. Two providers a long way apart on the headline figure are usually within a few per cent once the deliverable is the same.

An ngs custom panel, and what designing one involves

A custom panel starts from a gene and region list and ends with probes or primer pools that cover it evenly. The design work is the part buyers underestimate: repetitive and high GC regions need extra or redesigned probes, pseudogenes have to be handled or they steal reads, and coverage uniformity is what decides whether a variant at the edge of an exon is callable. Expect a design iteration after a pilot run, ask what the vendor's redesign policy is, and lock the panel version into the report, since a v2 panel is a different assay.

library preparation ngs runs on, and where it fails

Library preparation converts nucleic acid into a sequenceable pool, and almost every sequencing failure begins there. Input quantity and quality set the complexity: too little DNA gives duplicates, degraded input gives short inserts. Fragmentation sets the insert size, adapter ligation sets the index and any molecular barcode, and the bead cleanups decide whether adapter dimers reach the flow cell. Quantification and equimolar pooling decide whether every sample gets its share of reads. A pool checked on a fragment analyser and by a quantitative method before loading is what prevents a wasted run.

An ngs sequencer, and what choosing one commits you to

A sequencer is a chemistry, a consumable supply and a data footprint as much as an instrument. Read the flow cell or cartridge sizes, since output only pays when a run is full; the read lengths at the quality you need; the error profile, which differs between chemistries and matters for homopolymers and structural variants; and the library kits validated on it. Then the practical questions: service coverage, whether a second instrument can share consumables, and where the data will live.

Common questions

What should I check before choosing an NGS testing provider?

The panel content against your genes and the regions within them, the validated limit of detection and the sample types it was validated on, the accreditation appropriate to your use, and the policy on sample failures.

What is the difference between research and clinical NGS testing?

They operate under different regimes. In the United States, testing that informs a clinical decision must come from a laboratory under the clinical laboratory improvement regime; a research result cannot be repurposed however good it is technically.

What should an NGS report contain?

The regions covered and those that failed coverage, variants with their fractions, the limit of detection applied, and an explicit statement of what the test does not cover. Absence of a finding means nothing without that.

Can fixed tissue be used?

Usually, with constraints. Fixation fragments and chemically damages nucleic acid, so yields are lower and some approaches are unavailable. Declare the sample type at quoting rather than at the laboratory.

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