Diagnosis and Clinical Utility of Creatine Kinase-MB

Introduction to Creatine Kinase-MB

Creatine Kinase-MB (CKMB) is a cardiac-specific isoenzyme of Creatine Kinase (CK), with CKMB being more specific but less sensitive than cardiac troponins for detecting myocardial injury, while total CK is a non-specific marker found in both cardiac and skeletal muscle 1

CK-MB is a specific isoenzyme that has historically been the standard marker for myocardial infarction diagnosis before troponins became available 1
Total CK is found in high concentrations in both cardiac and skeletal muscle, making it less specific for cardiac injury 2
Low levels of CK-MB can be found in the blood of healthy persons, and elevated levels can occur with damage to skeletal muscle, limiting its absolute cardiac specificity 1

CK-MB is more specific for myocardial injury than total CK but less specific and sensitive than cardiac troponins 1, 3
CK-MB has a shorter half-life than troponin, making it useful for detecting early reinfarction (recurrent MI) when troponin levels are still elevated from the initial event 1
CK-MB is also valuable in diagnosing periprocedural myocardial infarction following interventions, as its diagnostic and prognostic value has been extensively validated in these situations 1

Both CK and CK-MB can be detected in blood 4-6 hours after myocardial injury, with peak levels occurring at 18-24 hours 4
CK-MB returns to normal within 36-48 hours, while troponins may remain elevated for 5-14 days 1
This shorter half-life of CK-MB compared to troponin allows for detection of reinfarction that might be missed if only troponin is measured 5

Cardiac troponins have largely replaced CK-MB as the preferred biomarker for diagnosing myocardial infarction due to their superior sensitivity and specificity 3
CK-MB remains useful in specific clinical scenarios, including diagnosis of reinfarction and evaluation of periprocedural myocardial injury during cardiac interventions 1, 5
The American Heart Association recommends using CK-MB in specific clinical scenarios, such as diagnosis of reinfarction and evaluation of periprocedural myocardial injury during cardiac interventions 1

CK-MB should be measured by mass immunoassays rather than older methods for optimal accuracy 1
Point-of-care testing systems are available for both markers but require stringent quality control 6

Elevated total CK without elevated CK-MB suggests skeletal muscle injury rather than cardiac injury 3
Older non-specific markers like alanine transaminase, aspartate transaminase, and lactate dehydrogenase should be avoided for cardiac evaluation in contemporary practice 1