Summary of Clinical Recommendations Based on Demonstrated Diagnostic Performance but without Data on Clinical Impact

All technologies reviewed had some published evidence of diagnostic performance and nine technologies had no studies of actual impact on clinical care (i.e., all clinical impact grade NK). The Working Group strongly advises that, with the exception of the standard 12-lead ECG (see immediately below), diagnostic performance alone is an insufficient basis for recommendation for general use. This is from the long experience of numerous examples of technologies that have excellent or good diagnostic performance, but negligible or even negative clinical impact when tested under conditions of actual use.

The standard 12-lead ECG has been shown in many studies to have very good, although not perfect, diagnostic performance in the ED. Given that the ECG is part of standard ED evaluation, in the view of the Working Group, a trial to demonstrate its clinical impact would be neither necessary nor ethical. Indeed, the 12-lead ECG should be part of the very initial evaluation of any ED or EMS patient with symptoms suggestive of ACI.

Although they have not yet been demonstrated to actually improve clinical care in high-quality studies, blood biochemical tests of myocardial necrosis have undergone prospective testing of their diagnostic performance for the detection of AMI. Available data suggest that the use of a single biomarker test yields insufficient performance for use in ED triage, but that the use of multiple tests over several or more hours has very good diagnostic performance for AMI. Combinations of differing assays, such as myglo-bin and CK-MB, performed serially have been found to yield excellent diagnostic performance. Myoglobin may be best suited to complement either CK-MB or a cardiac troponin in combination testing. It is important to bear in mind that none of the bio-markers have good sensitivity for UAP, which raises the possibility of missing this form of ACI if triage is dependent on such tests. Given the paucity of prospective trials of the impact of these tests on ED triage (level of admission or discharge), they cannot yet be recommended for general ED triage use at this time, although they are very useful for the diagnosis of AMI in observation units or in-hospital care.

Echocardiography, well studied in other settings, has undergone several studies in the ED, which have generally shown moderate diagnostic performance for initial ED evaluation. Given this, and that its actual impact on ED care has not been evaluated, this technology cannot be recommended for general ED use at this time.

Sestamibi and other technetium-99m perfusion agents have been studied in the ED setting, and although the overall diagnostic performance of sestamibi has been promising, it has not been sufficiently tested to recommend its general ED use. Whether ses-tamibi will be found to be more helpful when evaluated for special subgroups, and when tested for its actual impact on care, remains to be seen. At this point, its general ED use cannot be recommended.

As an extension of the standard ECG, nonstandard ECG leads have undergone some limited testing in the ED for detecting AMI, and another prospective trial was just completed. The good-quality (B) studies indicate that there is a small improvement (+) in diagnostic accuracy afforded by these leads. Since their impact on care has not been studied, nonstandard ECG leads cannot yet be recommended for general use. In a similar fashion, good-quality (B) studies of continuous ECGs have also found that they make a modest improvement in the accuracy of the ECG, but their impact on care has not been studied. Therefore, this modality cannot be recommended for general use at this time.

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