Issue 27 / 18 July 2016

EXPERTS have welcomed guidance on the appropriate use of cardiac troponin testing in general practice, but medico-legal challenges remain, says a leading medico-legal adviser.

A narrative review, published this week in the MJA, outlined the most appropriate use of troponin testing in assisting the diagnosis of acute coronary syndrome in general practice, and the importance of having systems in place to urgently respond to the results.

The review said troponin testing should only be ordered in general practice for patients presenting with ischaemic symptoms that occurred more than 24 hours previously.

“If these patients have no high-risk clinical features and a normal echocardiogram, they may be assessed with a single troponin assay but should be referred urgently to hospital if the result is elevated,” they wrote.

Patients presenting with symptoms suggestive of acute coronary syndrome in the previous 24 hours or other high-risk features should be referred immediately to an emergency department, said the authors, who presented five case reports illustrating both appropriate and inappropriate test ordering.

The review was welcomed by Dr Helen Wilcox, senior lecturer in general practice at the University of WA and lead author of a study published in the MJA last year calling for more guidance for GPs in the ordering of troponin testing.

Dr Wilcox, who is also a practising GP, said the review answered many of the concerns raised in her group’s prospective cohort study, which found that one in five GP-initiated troponin tests were ordered within 12 hours of symptom onset.

“This article is the first we’ve seen that unequivocally states the clinical scenarios and the timeframes in which troponin should and shouldn’t be ordered,” Dr Wilcox told MJA InSight. “It’s also the first article that talks about the role of high-sensitivity troponin in general practice.”

Dr Walid Jammal, Senior Medical Advisor – Advocacy with Avant, also welcomed the narrative review as an important contribution to the discussion about the role of cardiac troponin testing in general practice, but said it was unlikely to reduce the associated medico-legal risk.

He said there were several medico-legal challenges associated with the use of cardiac troponin testing in general practice.

“Problems may arise if the GP doesn’t properly understand the clinical utility and the positive and the negative predictive values of the test in a particular patient. This can lead to inappropriately ordering the test in patients for whom it’s not relevant,” he said. 

“Medico-legal risk will also arise if the GP doesn’t appreciate the time-critical nature of the test, or the GP doesn’t have a system in place to follow up the test in a timely fashion. Also, if the GP hasn’t forewarned the patient of the steps following both a positive and negative result.”

Dr Jammal said he didn’t see the issue as being as “black and white” as suggested by the review authors.

“In the absence of firm guidelines, it contributes to the discussion, but I wouldn’t say it provides firm medico-legal guidance.”

Lead author Professor Constantine Aroney, director of cardiology at Brisbane’s Holy Spirit Northside Hospital, said medico-legal risk was present in any consultation, particularly when a patient presented with a life-threatening illness, such as acute coronary syndrome.

But he hoped the narrative review would simplify the utility of cardiac troponin testing in the community setting by assisting GPs to determine the patients for whom the test was most suitable.

“We need systems in place that can appropriately diagnose that patient and then triage that patient for treatment,” he said.

“Any patient with a suspected acute coronary syndrome within the previous 24 hours clearly should be sent to hospital by ambulance. But for symptoms occurring more than 24 hours previously, then it’s up to the doctor’s discretion whether they will still send them to hospital if they are concerned about their symptoms or do other diagnostic tests, such as a troponin, in patients considered to be at low risk.”

Professor Aroney said GPs were looking for guidance in the application of cardiac troponin testing in primary care.

“[GPs] see a lot of different clinical scenarios and for those patients with subacute presentations, the use of a single troponin test is a useful diagnostic tool,” he said.

However, Professor Aroney warned that the test was not the “be-all and end-all”.

“For instance, a negative troponin doesn’t entirely rule out unstable angina, which can occur with normal troponin levels.”

Professor Aroney said that when ordering tests, it was incumbent on all physicians to have systems in place to respond to the results, and this was particularly so for cardiac troponin tests.

“A troponin test shouldn’t be ordered unless a doctor is available to review the result as soon as it is available,” he said. However, he noted that cardiac troponin test results were usually returned rapidly – often within an hour – allowing GPs to quickly refer patients with positive results to hospital or a cardiologist. 

Dr Wilcox noted that, in her study, the turnaround time for troponin results was variable, ranging from 2 hours to 2 days, even for tests that were marked urgent.

“We found that troponin should be ordered only when the results were able to be made available urgently,” she said.

Troponin testing was a useful tool to enable GPs to fulfil their gatekeeper role, Dr Wilcox said. “GPs are in a difficult situation, because we see a fair number of presentations of chest pain that theoretically could include acute coronary syndrome, and headache that could include raised intracranial pressure, but we still have that gatekeeper role, whereby we have to avoid over-investigation and saturating tertiary services with patients,” she said.  “So this latest review is really valuable.” 

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