Answer is C (Creatinine phosphokinase) Creatinine phosphokinase is seen at 4 to 8 hours (May be seen at 2-4 hours), peaks at 24 hours and return to normal by 72 hours. Creatinine phosphokinase MB (CPKMB) Very sensitive (CPK MB isoenzyme increases the specificity) 'Absence in change in levels of CPK and CPKMB during the 1st 2 days essentially excludes the diagnosis of MI' -Chandrasoma CK elevation used to be test of choice in First 24 hours. ('Cardiac troponins are now preferred'). CKMB is still the test of choice for detecting recurrent ischaemic event.