A CK-MB mass/total CK activity ratio cutoff of 80 ng/U differentiated acute myocardial infarction (mean maximum >200 ng/U) from muscular injury (highest ratio 38 ng/U, excluding one infant).
Observational (n=69)
Does the serum CK-MB mass/total CK activity ratio differentiate myocardial necrosis from muscular injury?
A CK-MB/total CK ratio cutoff of 80 ng/U effectively differentiates myocardial infarction from skeletal muscle injury.
We immunoenzymometrically measured creatine kinase (CK) isoenzyme MB in extracts of myocardium and in homogenates of five different skeletal muscles. CK-MB concentrations in the former averaged 80.9 micrograms/g wet tissue; in the skeletal muscles it varied widely, being (e.g.) 25-fold greater in diaphragm than in psoas. CK-MB in skeletal muscles ranged from 0.9 to 44 ng/U of total CK; the mean for myocardium was 202 ng/U. In sera from 10 trauma and 36 burn patients without myocardial involvement, maximum ratios for CK-MB mass/total CK activity averaged 7 (SEM 1) ng/U and 18 (SEM 6) ng/U, respectively. Except for an infant (220 ng/U), the highest ratio we found for serum after muscular damage was 38 ng/U. In contrast, the mean maximum ratio determined in 23 cases of acute myocardial infarction exceeded 200 ng/U. Among seven determinations performed 8 to 32 h after onset of symptoms, each infarct patient demonstrated at least one ratio greater than or equal to 110 ng/U. Ratios observed after infarct were unrelated to treatment received during the acute phase. We propose a CK-MB/total CK ratio of 80 ng/U as the cutoff value for differentiating myocardial necrosis from muscular injury.
Allaf et al. (Sat,) conducted a observational in Myocardial infarction vs muscular injury (n=69). CK-MB mass/total CK activity ratio vs. Muscular damage was evaluated on CK-MB mass/total CK activity ratio. A CK-MB mass/total CK activity ratio cutoff of 80 ng/U differentiated acute myocardial infarction (mean maximum >200 ng/U) from muscular injury (highest ratio 38 ng/U, excluding one infant).