Creatine Kinase Is Not Part of a Comprehensive Metabolic Panel
Creatine kinase (CK) is not included in a standard comprehensive metabolic panel (CMP). A comprehensive metabolic panel typically includes glucose, sodium, potassium, chloride, carbon dioxide, blood urea nitrogen (BUN), creatinine, calcium, alkaline phosphatase (ALP), alanine transaminase (ALT), aspartate transaminase (AST), bilirubin, albumin, and total protein 1.
Components of a Comprehensive Metabolic Panel
The CMP consists of 14 standard tests that provide important information about:
Electrolytes and fluid balance:
- Sodium
- Potassium
- Chloride
- Carbon dioxide (bicarbonate)
Kidney function:
- Blood urea nitrogen (BUN)
- Creatinine (not to be confused with creatine kinase)
Liver function:
- Alkaline phosphatase (ALP)
- Alanine transaminase (ALT)
- Aspartate transaminase (AST)
- Bilirubin
- Albumin
- Total protein
Metabolic status:
- Glucose
- Calcium
Where Creatine Kinase Is Measured
Creatine kinase is measured separately as a specific test when there is concern for:
- Muscle damage or injury 2
- Myocardial infarction (particularly the CK-MB isoenzyme) 3
- Certain neuromuscular disorders
- Monitoring for medication side effects (such as statin-induced myopathy) 1
Clinical Significance of Creatine Kinase
Creatine kinase is an enzyme found primarily in the heart, skeletal muscles, and brain 4. It catalyzes the reversible transfer of a phosphoryl group from phosphocreatine to ADP, playing a crucial role in cellular energy metabolism 5, 6.
The three main isoenzymes of CK are:
- CK-MM (skeletal muscle)
- CK-MB (cardiac muscle)
- CK-BB (brain)
When to Order Creatine Kinase Testing
Creatine kinase should be ordered separately when evaluating:
- Suspected myocardial injury (though troponin has largely replaced CK-MB for this purpose)
- Rhabdomyolysis
- Muscular dystrophies
- Inflammatory myopathies
- Monitoring for drug-induced myopathy (particularly with statins)
- Immune-related adverse events from immunotherapy 1
Common Laboratory Panels That Include CK
While CK is not part of the standard CMP, it may be included in:
- Cardiac enzyme panels (though increasingly replaced by troponin)
- Muscle damage assessment panels
- Specialized immunotherapy toxicity monitoring panels 1
Key Takeaway
When ordering laboratory tests to evaluate basic metabolic status, remember that creatine kinase requires a separate order beyond the standard comprehensive metabolic panel. Do not confuse creatinine (which is part of the CMP and measures kidney function) with creatine kinase (which is a separate enzyme test for muscle damage).