Cardiac
Troponin (cardiac troponin I/T)
Cardiac troponins are regulatory proteins released into the bloodstream when heart muscle is injured, making them the central biomarker for diagnosing acute myocardial infarction. Point-of-care troponin testing brings this measurement to the patient side, supporting rapid chest pain rule-in and rule-out pathways in emergency departments, ambulances and primary care.
Why it is measured
Troponin is the most cardiac-specific and sensitive blood marker of myocardial injury, underpinning the internationally recommended 0/1-hour and 0/3-hour chest pain algorithms. Delivering a result near the patient can shorten time to clinical decision in time-critical settings.
| Typical range | Results are interpreted against the assay-specific 99th percentile upper reference limit, not a conventional reference interval. For high-sensitivity cardiac troponin I on a point-of-care platform such as the Siemens Atellica VTLi, the 99th percentile in adults is approximately 18 ng/L in women and 23 to 27 ng/L in men, with values below this generally regarded as normal. Contemporary (non high-sensitivity) point-of-care assays use higher cut-offs reported in different units, for example the Abbott i-STAT cTnI cut-off of around 0.08 ng/mL (equivalent to 80 ng/L). Cut-offs, units and sex-specific thresholds vary by method and manufacturer, so always apply the values validated for the specific analyser and population in use. |
|---|---|
| Sample | Whole blood, typically lithium heparin, applied directly to a cartridge or test cuvette; some platforms also accept plasma. Sample volumes are small, often a few drops to under 200 microlitres. |
| Turnaround | Approximately 8 to 20 minutes from sample application to result, depending on the platform. |
Point of care devices that report it
- Siemens Atellica VTLi (whole-blood high-sensitivity cardiac troponin I, patient-side immunoassay analyser)
- Abbott i-STAT cTnI cartridge (quantitative whole-blood cardiac troponin I)
- Abbott i-STAT hs-TnI cartridge (high-sensitivity cardiac troponin I)
- Radiometer AQT90 FLEX (point-of-care cardiac troponin I and troponin T immunoassays)
- Roche cobas h232 (handheld reader for cardiac troponin T, a contemporary not high-sensitivity assay)
Questions, answered
Is a point-of-care troponin result as reliable as a central laboratory troponin?
Point-of-care troponin platforms can perform well and several whole-blood assays now meet high-sensitivity criteria, but each method has its own cut-offs, units and analytical characteristics, so results are not directly interchangeable between devices. Good practice is to validate the analyser locally, run regular internal quality control and external quality assurance, and apply only the cut-offs verified for that specific platform rather than transferring thresholds from a laboratory analyser.
Why are high-sensitivity troponin results reported in ng/L and what does the 99th percentile mean?
High-sensitivity assays can detect very low troponin concentrations, so results are reported in nanograms per litre (ng/L) to give useful resolution at low levels, whereas older assays often used micrograms per litre or ng/mL. The 99th percentile upper reference limit is the concentration below which 99 percent of a healthy reference population falls, and it is used as the decision threshold instead of a traditional reference range; many assays also publish separate male and female limits.
Can a single troponin measurement rule out a heart attack?
Troponin is interpreted within structured protocols rather than from one number in isolation. Many pathways use serial sampling, such as 0 and 1 hour or 0 and 3 hours, looking at both the absolute value and the change between samples, alongside the clinical picture and the electrocardiogram. Interpretation for an individual is a clinical decision and should follow the relevant local chest pain protocol.