Reference
qPCR and shotgun metagenomics for oral testing
Targeted qPCR and shotgun metagenomic sequencing are two laboratory methods for describing the oral microbiome. qPCR measures a predefined list of targets and quantifies each one. Shotgun sequencing reads the DNA present without a predefined list and reports what proportion of the community each organism represents. Neither is the better method in general; they answer different questions, and both are interpreted alongside a clinical examination.
What shotgun metagenomics does that qPCR cannot
Shotgun sequencing does not need to know what it is looking for. It reads the DNA in a sample and identifies what is there, which means it can find organisms nobody thought to include on a panel.
It also resolves organisms finely and can describe functional gene content across the whole community — the genes a community carries, not just which organisms are present. Metagenomic sequencing of periodontal samples has been used in exactly that way, to describe both the microbiota and its functional potential in periodontal disease.
A targeted panel cannot do either of those things. It reports what it was designed to look for, and nothing else. If the clinically relevant organism is not on the panel, a targeted assay will not find it, however much of it is present.
What targeted qPCR does that sequencing does not
A targeted assay measures a specific sequence against a known standard, which makes its output a quantity for that target rather than a share of a total.
That distinction matters more than it sounds. Sequencing output is compositional: it reports each organism as a proportion of the reads in that sample. A change in one organism's proportion can occur because that organism changed, or because something else did. This property of sequencing data is well described in the literature and is a statistical feature of the method rather than a flaw in any particular product.
Targeted assays are also generally faster and cheaper per sample, because they sequence nothing and require far less computation. Where a defined set of organisms is the clinical question, that is a real advantage.
Where each method is stronger
Both are DNA methods applied to the same kind of sample. Neither measures a clinical outcome.
| Question | Targeted qPCR | Shotgun metagenomics |
|---|---|---|
| Can it find an organism not on the list? | No | Yes |
| Does it report a quantity or a proportion? | Quantity, against a standard | Proportion of reads |
| Does it describe community function? | Only for genes explicitly targeted | Yes, across the community |
| Resolution | The targets chosen, at the level designed | Species and often strain |
| Turnaround and cost per sample | Generally faster and lower | Generally slower and higher |
| Interpretation burden | Bounded — a fixed set of results | Higher — large result sets need reduction |
Why OraPath uses targeted qPCR, and what that costs
OraPath's panels are targeted qPCR. The reason is the use case rather than a view that sequencing is inferior: the panel exists to give a clinician a bounded, quantified set of results with a turnaround that fits a recall interval, and to make a follow-up sample directly comparable to the first.
That choice has real costs, and they should be stated rather than glossed.
A targeted panel cannot surprise you. It will never report an organism it was not designed to detect, so an unusual finding outside the panel is invisible to it. It also describes far less of the community than a sequencing method does — sixteen targets is not a census of a mouth that contains hundreds of species.
Where 16S sequencing sits
16S rRNA gene sequencing is a third approach, and the one most often meant by “sequencing” in consumer microbiome testing. It amplifies a single marker gene rather than all DNA present.
It is cheaper than shotgun sequencing and gives broad community coverage, but it typically resolves organisms less finely and does not read functional gene content across the community. Shotgun sequencing has been reported to capture more diversity than 16S on the same specimens.
What neither method establishes
Both methods describe the DNA in a sample. Neither observes a disease, and neither establishes that an organism is causing anything a patient is experiencing.
Any result from either approach is interpreted alongside an examination and a patient's history. The Oral Balance Test is a laboratory developed test performed by IMMYLabs under CLIA; it has not been cleared or approved by the FDA, and it is intended to support a clinician's assessment rather than replace one.