Issue 40 / 19 October 2015

GPs should maintain a high threshold for requesting cardiac troponin testing and promptly refer patients with suspected acute coronary syndrome, according to researchers.
A prospective cohort study of 124 GP-initiated cardiac troponin (cTn) tests, published in the MJA, found that based on clinical risk factors, 71 of 104 patients (69%) were at high or intermediate risk of acute coronary syndrome (ACS). It also found that 69 of 124 patients (55.6%) had typical ischaemic pain and 62 of 124 patients (50.0%) were tested within 48 hours of symptom onset ACS. (1)
While 122 of the 124 cTn results in the study were negative, the researchers said it did not rule out the possibility of ACS, with 3.7% of patients (13/355) admitted to hospital with an ACS within 30 days of receiving a negative result.
“Possible ACS is one setting in which GPs can justifiably advise patients to present to a hospital, rather than undertaking investigations in primary care”, the researchers said.
Professor Mark Nelson, chair of the discipline of general practice at the University of Tasmania, said the researchers’ conclusions were warranted and considered.
He told MJA InSight that, like any diagnostic test, the agility of cTn testing depended on pre-test probability. “If there is a high pre-test probability [of ACS], there’s really no sense in doing the test.
“If someone has typical chest pain, if it’s not stable angina, they should go to an emergency department, because they’re the ones who need acute care.”
Professor Nelson said ordering the test, often based on a patient request, where there was low clinical suspicion of ACS was also not useful in primary care.
“If [the result] does come back marginal, then it’s unlikely to indicate clinical disease and it’s just going to confuse matters.”
The MJA researchers wrote that GPs might not fully understand the limitations of cTn testing, as 23.4% of tests in their study were ordered within 12 hours of symptom onset, “at which point the test may be insufficiently sensitive”.
“While all major guidelines groups recommend serial testing to exclude ACS in this context, no serial testing was performed by GPs in our study”, they wrote.
In many cases, the test result did not alter patient management.
The researchers also highlighted the difficulties faced by GPs in dealing with patients with suspected ACS.
“The consequences of missing an ACS diagnosis can be grave, yet there are no reliable clinical predictors of ACS, and primary care investigations have their limitations. At the same time, GPs have an important role as gatekeepers of the health system”, they wrote.
Professor Nelson agreed that GPs were often in a difficult situation and were sometimes criticised for ready referral, but the stakes were high in cases of suspected ACS.
“If people have clinical symptoms or signs of having an ACS, it’s not something that should be managed in primary care, except in certain rural and remote circumstances, which isn’t discussed in this paper”, he said.
The researchers included only samples collected at urban practices, acknowledging that rural and regional practices were likely to have different approaches to cTn testing.
Professor Derek Chew, director of cardiology at Southern Adelaide Local Health Network, said general practices managing patients with suspected ACS needed to develop models of care to effectively deal with the results of cTn testing.
“If you embed tests into a practice that is not designed to deal with the result of the test, this is what you are going to see”, he said of the MJA research findings.
“I am not saying that primary care can’t do this; I am saying that primary care needs to be designed to do this if they want to do it.”
Professor Chew, who coauthored an MJA editorial last year about the potential for cTn and the challenges of its use in primary care, said the diagnostic tests were a very effective tool in assessing chest pain when used within an appropriate model of care. (2)
He said GPs initiating cTn testing for patients presenting with chest pain should be able to provide and interpret electrocardiograms for all patients who presented with chest discomfort, chase cTn results in a timely manner and repeat assays as required.
Protocols for patients with positive test results and for those with negative results but with high suspicion also needed to be programmed into the system, Professor Chew said.
(Photo: Jarun Ontakrai / shutterstock)

4 thoughts on “Troponin test concerns

  1. Alfredo Aiello says:

    I firmly believe that the research on this matter is helpful but should not undererestimate common sense and knowledge of GPs.

    Troponin is useful as an extra tool. Same as ECG.

    All GPs know that the ABCs of ACS, and risk assessment: presenting complaint, history of presenting complaint, pain, risk factors, associated symptoms etc. will prevail.

    if serial troponins are not done there is no doubt that if the case merits or is borderline it will be dealt with appropriately. 

    Patient will then be referred to emergency department, cardiologist, stress test, discussion with specialist over the phone if opinion warented. Myocardial perfusion etc.

    This is not rocket science. 

    More like day to day “bread and butter” presentations.

    Misses and near misses are most likely to occur in busy EDs with 4 hour tolerance of moving patients out of ED.

    I work at both sides of the fence.

    I have found most doctors well trained and safe.






  2. Carlos Cobelas says:

    I disagree with the above comment by Fred.

    Someone with a suspected ACS should not be at home awaiting results of troponin.

    Too often we get patient told to come to ED because their troponin is raised.  The patient is at home and the blood test was taken 6 hours ago!!

    A suspected ACS should be sent to hospital.

    Misses in the ED these days are very rare as we keep people for excessive periods of time doing repeat troponins,  the vast majority of raised ones being false positives anyway.  

    Fred, the 4 hr target does not mean we discharge people inappropriately. They are admitted to the short stay unit for the repeat troponins.  The 4 hr target is not strictly followed and is often ignored in individual cases anyway

  3. Huw Clark says:

    I diagree with the ED dr above which is difficult in 1800 characters, especially when drugs trials are involved.

    The article makes a number of statements that reference 2006 guidelines. Alot has changed in the intervening years. As a start, they mention Clopidogrel but we’ve had Prasugrel and its composite end point, dodgy trial definitions and terrible haemorrhagic complications leading us into the brave new era of Ticagrelor.

    Sensitivities of trop testing have changed markedly allowing the 12 hour time frame to be reduced. Whoever performs the test, negative results preclude cardiology units from admitting anyone regardless of history or “disctinction” between the various risk groups that every guideline outlines. From that point on pts are “for provocative testing through the GP” as a glib shedding of responsibility to arrange for testing that is in itself imperfect and prone to misinterpretation and misuse. 

    All of that aside, what does a delay of a few hours actually mean to a patient with a positive result? The vast majority of patients remain perfectly well. The pain is gone, there’s no new heart failure and the incidence of malignant arrythmia seems low. There’s alot of bother generated by adherence to guidelines, the American one cites a 1988 study as the reason for Heparinisation post ACS yet that study was recanated in 1992 by the authors. The broader question is whether people who’ve had an ACS need to be admitted at all to hospital or whether outpatient management might be more cost effective with very little change in outcome? Perhaps GPs are actually better suited.

  4. Sue Ieraci says:

    “Another ED doctor” is spot on – EDs are relying too much on troponin testing, and not adequately screening patients for pre-test probability for acute coronoary syndrome. We are over-testing, over-diagnosing and over-referring, then, there is good evidence of over-stenting (stents being evidence-based for STEMI, but not for other conditions). We now define NSTEMI as a troponin rise – even in a well patient with normal ECG. So, the test defines its own outcome. What we really need to know is whether hospitalising patients with a raised troponin but normal ECG who are clinically well actually improves their outcomes, or whether they have more complications. We also need to know how standarised and how effective is the application by Cardiologists of medical therapy and interventional therapy.

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