Serial myoglobin quantitation in the early assessment of myocardial damage: A clinical study

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Objectives: (a) To evaluate serial serum myoglobin pattern as an early marker of myocardial damage and compare it to conventional enzyme markers, and (b) to test the hypothesis that a patient admitted within 6 h of the onset of chest pain who has normal myoglobin concentrations that do not increase significantly in the first 2 h has not suffered a myocardial infarction (MI). Design and methods: A clinical study was conducted including 98 patients (62 males, 36 females) who presented to our Emergency Department with a diagnosis of possible MI. Patients with chest discomfort were selected to participate in the trial if their ECG was equivocal, their diagnosis was not obvious, and their treatment in hospital was to be the same as a MI patient until proven otherwise. Myoglobin measurements were made on admission and at 1 and 2 h thereafter. Quantitative myoglobin assays were performed by fluorometric enzyme immunoassay (STRATUS). Traditional cardiac enzymes were also measured. Results: The myoglobin assay had good precision with CVs less than 10%. The sensitivity and specificity for MI of the myoglobin assay were 0.77 and 1.00 at 1 h and 0.93 and 1.00 at 2 h, respectively. Of positive diagnoses, 90% were clear 1 h after admission. Serial myoglobin assays provided better predictive efficiency (0.96) than baseline ECG (0.70) or CK-MB (0.62) in the admission assessment of possible MI patients. Conclusions: Negative myoglobin serial assays can be used effectively to rule out MI. Positive myoglobin serial assays help in the early diagnosis of MI in uncomplicated patients.