Outcomes of non-invasive diagnostic modalities for the detection of coronary artery disease: network meta-analysis of diagnostic randomised controlled trialsBMJ 2018; 360 doi: https://doi.org/10.1136/bmj.k504 (Published 21 February 2018) Cite this as: BMJ 2018;360:k504
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Re: Outcomes of non-invasive diagnostic modalities for the detection of coronary artery disease: network meta-analysis of diagnostic randomised controlled trials
The case for CT coronary angiography for all patients with stable chest pain has not been made.
The authors of the meta-analysis published in the BMJ are to be congratulated on this important piece of work.1 They conclude that the use of CT coronary angiography (CTCA) in patients with low risk ACS and stable chest pain is associated with a higher rate of downstream investigations, in the form of invasive coronary angiography, as well as a higher rate of revascularisations, without clear evidence of a difference in the incidence of myocardial infarctions. In the UK, the National Institute of Health and Care Excellence (NICE) reviewed the clinical trial evidence, and concluded that CTCA should be used in all patients presenting with stable chest pain.2
The cost effectiveness modelling that NICE undertook, demonstrated that CTCA was more cost effective than imaging stress tests. This however, was based on the price of a CTCA being £120. The actual tariff recommended by the NHS for CTCA in the UK is £220. Furthermore, the question NICE considered was how best to diagnose coronary artery disease (CAD). Given CTCA is a very sensitive test for the detection of CAD; it fulfils that role well. The caveat is that CTCA overestimates the degree of coronary stenoses, hence the higher rate of downstream testing. The higher rate of revascularisation, in studies comparing CTCA with stress tests, can be explained by the higher sensitivity for CTCA, but the important point, is that there was no difference in outcome.
The SCOT-Heart study is often quoted as the evidence of superiority of CTCA over stress tests because there was a trend towards lower event rate in the CTCA arm. However, SCOT-Heart compared CTCA plus Exercise ECG vs. Exercise ECG. This is a comparison of anatomy plus stress testing vs. stress testing.3 Furthermore, the accuracy of Exercise ECG is inferior to the imaging stress tests as demonstrated in this meta-analysis.
NICE recognised that recommending CTCA for all patients may lead to an increase in the downstream testing with invasive coronary angiography and hence have recommended, in a separate guideline, CT fractional flow reserve (FFR), a £700 test which uses the CTCA data to calculate a FFR, based on computational fluid dynamics.4 CT-FFR correlates reasonably well with invasive FFR. Invasive FFR is an established functional test used during invasive coronary angiography to decide if a coronary stenosis is causing ischaemia.
PLATFORM, the largest CT-FFR trial to date (n=585) compared CTCA plus CT-FFR vs. the standard of care. The end point of the study was reduction of invasive coronary angiography that showed no obstructive CAD. The patients were divided into an invasive sub-study (n=380) and a non-invasive sub-study (n=204). In the invasive sub-study, CTCA plus CT-FFR reduced the rate of invasive coronary angiography as only patients found to have significant stenosis and positive CT-FFR went on to have invasive coronary angiogram, while in the invasive arm all patients had to undergo invasive coronary angiogram ± invasive FFR. In the non-invasive sub-study there was no difference in the rate of invasive coronary angiography between imaging stress tests and CTCA plus CT-FFR.5 It is important to emphasise that imaging stress tests cost a fraction of the cost of CTCA plus CT-FFR.
1. Siontis GC, Mavridis D, Greenwood JP et al. Outcomes of non-invasive diagnostic modalities for the detection of coronary artery disease: network meta-analysis of diagnostic randomised controlled trials. BMJ. 2018 Feb 21;360:k504. doi: 10.1136/bmj.k504.
3. SCOT-Heart investigators. CT coronary angiography in patients with suspected angina due to coronary heart disease (SCOT-HEART): an open-label, parallel-group, multicentre trial. Lancet 2015;385:2383-2391
5. Hlatky MA, De Bruyne B, Pontone G, et al. PLATFORM Investigators. Quality-of-Life and Economic Outcomes of Assessing Fractional Flow Reserve With Computed Tomography Angiography: PLATFORM. J Am Coll Cardiol 2015;66:2315-2323.
Competing interests: No competing interests