CK-MB assays used in cardiac damage diagnosis are immunoassay measurements rather than enzyme assays that measure the activity of CK-MB itself. Recall that although CK-MB is specific, it is also present in skeletal muscle; therefore, skeletal muscle injury can cause CK-MB elevation. Some laboratories measure total CK and if elevated, reflex to CK-MB testing.
Normal CK-MB values
for adults are typically < 5.0 ng/mL.