Method: A decision analytic model was developed to estimate the cost-effectiveness of diagnostic strategies for assessing patients with ischaemic cardiomyopathy. The different diagnostic pathways were applied to a hypothetical cohort of patients with ischaemic cardiomyopathy and the probability of successful identification of viable myocardium and non-viable myocardium was determined by the accuracy of the diagnostic pathway. It was assumed that patients diagnosed with viable myocardium would be managed promptly by revascularisation and that the patients diagnosed with non-viable myocardium would be on medical therapy. The model assigned each patient a risk of death and rehospitalisation depending upon whether they are truly viable and whether they had revascularisation or not. Each patient then accrued lifetime QALYs. Health care costs were also accrued through measuring diagnostic costs and treatment costs, depending on the pathway and their treatment status.
Result: All the diagnostic pathways are cost-effective when compared with no testing at current NICE threshold, this suggests that all the current services for diagnosing viable myocardium are a cost effective use of NHS resources irrespective of the diagnostic pathway used. For services that need to decide the most cost-effective strategy starting from scratch, then Stress CMR is the most cost-effective strategy.
Conclusion: There are a number of issues with abstracting the data for cost-effectiveness modelling of diagnostic tests. For example, the diagnostic accuracy depends upon the type of index test, gold standard test and threshold used. Furthermore, the benefits of treatments after diagnosis are not always clear and might be linked to the type of diagnostic test. Appropriate caution needs to be taken when evaluating diagnostic tests.
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