Objectives The introduction of high sensitivity troponin (hs-Tn) redefines who is diagnosed with myocardial infarction (MI) and may increase the incidence of MI. The Preventing Overdiagnosis Working Group of the Guidelines International Network recently published a checklist for groups seeking to modify a disease definition in 2017. We used the checklist to determine if this clarifies the harms and benefits of the new test in the diagnosis of MI.
Method We assessed the evidence for hs-Tn against each of the questions in the 8-item checklist:
Differences between the previous and the new definition
Changes to the incidence and prevalence of the disease
Trigger for considering the modification
Does it predict clinically important outcomes compared with the previous definition?
What is the repeatability, reproducibility, and accuracy of the new disease definition?
Benefit: What is the incremental benefit for patients?
Harm: What is the incremental harm for patients?
What is the net benefit and harm for patients?
Results hs-Tn has higher analytical sensitivity, which allows myocardial infarction to be diagnosed earlier and treatment commenced. Patients with low levels at 4 hours can be safely discharged. hs-Tn also is predictive of clinically important outcomes and has higher precision than earlier forms of the troponin. Maintaining the 99th centile as the threshold for diagnosis of myocardial infarction and the methods used in studies to determine the reference limit leads to an increase in the numbers of people diagnosed with myocardial infarction, with significant differences between studies depending on the types of patients being tested. The evidence for assessing the benefits and harms of hs-Tn is limited, limited to a before-after study showing an improvement in health outcomes. The introduction of hs-Tn in Australia earlier than in the US may explain the divergence in the incidence of non-ST elevation myocardial infarction in the two countries.
Conclusions The example of hs-Tn illustrates that rigorous evaluations of disease definitions cannot be isolated from the tests used to diagnose that disease. Despite the significant consequences from the introduction of the test and the potential for overdiagnosis, it has been introduced because of improvements in analytical performance rather than on a thorough evaluation of potential harms and benefits.
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