CORE-ABR
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Topic · PCR

PCR and qPCR reporting

Real-time PCR tells you more than positive or negative. CORE-ABR puts the Ct, the limit of detection and the load on the page, so a faint detection reads differently from a dominant one.

Gloved hand loading a PCR tube into a strip in a real-time PCR thermocycler
Real-time PCR: the Ct value, limit of detection and cycles above LOD all come from this run.

From Ct to something a clinician can read

In quantitative (real-time) PCR, the cycle threshold (Ct) is the amplification cycle at which a target's signal crosses the detection threshold. Lower Ct means more starting target. On its own, a Ct value means little to an ordering clinician. CORE-ABR reports it alongside:

  • The assay's limit of detection (LOD) for that target.
  • Cycles above LOD — how far inside the detectable range the result sits.
  • A load band (for example high, medium, low) with gene copies per mL where the assay supports quantification.

That context matters most for organisms that can be either cause or bystander — Staphylococcus epidermidis, Cutibacterium acnes, Candida — where quantity is part of the argument.

Organisms are quantified; genes are qualitative

Resistance genes are reported as detected or not detected. A multiplex panel cannot tell you which organism in a mixed specimen carries a detected gene, which is why CORE-ABR applies each gene only to the organisms known to carry it — see how grading works.

Tested and not detected

Every target the panel interrogated is listed, including those not found. The reader never has to wonder whether something was looked for. A negative result is information: a panel with no mecA keeps beta-lactams in play.

Pooled targets

Some PCR wells detect more than one species together — for example Enterococcus faecium / faecalis. CORE-ABR reports these the way the assay does and states the limitation on the report, rather than implying a species-level call the assay did not make.

Molecular detection does not replace culture or phenotypic susceptibility testing, and it does not replace public-health reporting obligations.

PCR targets

Resistance gene targets

Decision support only. The treating clinician decides. Molecular genotype does not replace phenotypic susceptibility testing, culture, or public-health reporting. Absence of a detected resistance gene does not establish susceptibility. Organism targets vary by panel; CORE-ABR is configured to the assay each laboratory runs.