NHS Western Isles guidelines - In development
- Troponin I is a cardiac specific protein. Any cause of myocyte damage will release troponin I. It does not indicate the mechanism of myocyte damage.
- Troponin I using the current lab High Sensitivity method will be detectable in the blood in 1 hour after injury.
Troponin I: guide for primary care
Procedure for requesting Troponin I
Take sample in Red EDTA tube and note time taken and time of onset of symptoms.
- The sample must be processed within 4 hours of being taken.
- Contact the Lab (9-5 Mon-Fri, 9-12 Sat-Sun). Out with these hours contact A+E to run the sample (OUAB and St Brendan’s also have access to POC testing on site)
- Ensure that you leave clear instruction of where the result should be telephoned to.
- For Interpretation see
- Intranet> Shared Clinical Guidelines Homepage> Top Left Red Box ‘Trop I Algorithm’.
Troponin I will be raised by any condition that causes myocyte damage. It is therefore a very NON-SPECIFIC test for Myocardial Infarction but is also very sensitive. Examples of conditions that can raise Troponin I include:
- Heart Failure (Acute or Chronic)
- Tachy/Brady arrhythmias (e.g. Fast AF, SVT)
- Hypertrophic Cardiomyopathy
- Hypertension
- PE
- COPD
- Renal Impairment
- Troponin I can aid a diagnosis of MI but must never be used in isolation to do so
- MI evaluation and diagnosis requires careful clinical evaluation and ECG analysis as well as assessment of cardiac biomarkers such as Troponin I
- As Troponin I can be persistently raised in many individuals (e.g. with renal impairment or heart failure), the diagnosis of myocardial damage requires a dynamic change in Troponin I in the blood. Therefore, myocardial damage can only be reliably diagnosed by taking TWO readings separated by a time interval. A single raised reading is insufficient to exclude myocardial damage in most cases.
- A single reading taken more than 3 hours after an episode of chest pain however can reliably rule out Myocardial Infarction if it is not raised as Troponin I becomes detectable by about 1 hour following Myocardial Damage.
- With very few exceptions (examples below), Troponin I should only be requested in a secondary care
- Examples of when it may be appropriate to request a Troponin I in primary care would include:
- A patient with an equivocal history who is deemed unsuitable for transfer for PCI or ‘Intensive’ treatment but in whom knowledge of a recent MI would allow appropriate treatment to be commenced
- A stable patient who presents ‘late’ after an episode of chest pain who declines admission but in whom a Troponin I result confirming MI would affect treatment/refer