Macro CK in patients with elevated troponin I levels

CK-MB activity levels can be falsely elevated by the presence of macro CK, especially if immuno-inhibition assays are used in the measurement. In patients with macro CK and cardiac pathology that could result in an elevated CK-MB activity, the diagnostic challenge lies in determining the true cause of the elevated CK-MB activity. We present two case reports of patients with elevated CK-MB activity and troponin I levels, but who subsequently had CK-MB activity higher than total CK activity, raising the suspicion of the presence of macro CK.