We appreciate the comments of Drs. Reilly and Evans and agree that decisions must be based on the potential benefits of subsequent interventions rather than on diagnosis alone. However, accurate diagnosis often must precede appropriate therapy. For acute chest pain, the initial triage should provide urgent therapies of known benefit: recanalization with primary angioplasty or thrombolysis for ST-segment elevation acute MI and interventions to prevent infarction or limit its size in patients with non–ST-segment elevation acute coronary syndromes. An accurate reading of the initial electrocardiogram is critical to guide these interventions and to determine the most appropriate setting for observation and rapid treatment if complications occur. The "ruling out" of MI certainly is not the sole quality benchmark but is linked to management strategies proven to improve outcomes. If a patient is mistakenly discharged, the opportunity to provide these benefits is delayed or lost.

A single biomarker assay in the emergency department has inadequate sensitivity to exclude MI or adverse outcomes. We believe the decision to obtain a biomarker level requires a commitment to 1) admit a patient with positive results and 2) provide sufficient observation for a patient with negative results, generally 6 hours, at which time a second biomarker level is required. Newer biomarkers may further inform risk stratification (1, 2). As the "rule out MI" paradigm evolves into a more finely tuned method of risk assessment, our prediction rule (3) allows an independent estimation to serve as a "prior probability" that can be modified by additional data.

Chest pain evaluation units increase the number of patients who are observed rather than discharged immediately, but an efficient, short-stay unit, preferably with predischarge stress testing, provides practical diagnostic and prognostic evaluation without the inconvenience, uncertainty, or risk of a delayed outpatient visit. For the type of patients who are observed, the choice is really "pay now or pay later."

We advocate strategies that can improve diagnostic sensitivity with acceptable costs and inconvenience by adopting systems of care rather than relying on the judgment of individual physicians, an approach that Dr. Reilly has championed at his own institution (4). Those who wish to move medicine forward must not abandon the elusive search for perfection despite its impossibility in daily practice.