We evaluated whether recent
cocaine use alters the specificity of CK-MB,
myoglobin, and cardiac
troponin I for acute
myocardial infarction (AMI) in patients who are seen in the emergency department for
chest pain. Patients <60 years old with potential
myocardial ischemia underwent a standardized history and physical examination and routine CK-MB assays every 8 to 12 hours and had study serum obtained at presentation for CK-MB,
myoglobin, and cardiac
troponin I immunoassays, as well as
benzoylecgonine,
cocaine's main metabolite. We enrolled 97 patients, 19 (20%) of whom had recent used
cocaine. Patients with and without
cocaine use were similar with regards to sex, race, renal and
muscular disease, diabetes, family history, and
hypertension and rate of AMI (12% vs 11%, p = 1.0). In patients without MI, the mean
myoglobin level was higher in
cocaine users than noncocaine users (179 vs 74 ng/ml; Mann-Whitney p = 0.003), but the mean values were similar for CK-MB (2.2 vs 2.1 ng/ml; Mann-Whitney p = 0.58) and for cardiac
troponin-I (0.02 vs 0.02 ng/ml; Mann-Whitney p = 0.87). The specificities of the markers in patients with and without
cocaine use were as follows: cardiac
troponin I, 94% vs 94%, (p = 1.0); CK-MB, 75% vs 88% (p = 0.24); and
myoglobin, 50% vs 82%, (p = 0.02), respectively. Our data demonstrate that the specificity of
myoglobin was altered by recent
cocaine use. The specificity of CK-MB was affected less and the specificity of cardiac
troponin I was not affected by recent
cocaine use.