Routine Creatine Kinase Testing: Not Recommended
Routine measurement of creatine kinase (CK) is not recommended unless the patient has muscle symptoms. 1
Evidence Against Routine CK Testing
- Guidelines do not recommend routine measurement of CK in individuals receiving statin therapy, but rather suggest it should be reserved for those with muscle symptoms 1
- With contemporary troponin assays, CK-MB and other markers are not useful for diagnosis of acute coronary syndromes 1
- Measurement of total CK is not recommended for the diagnosis of myocardial infarction due to its large skeletal muscle distribution and lack of specificity 1
When CK Testing May Be Appropriate
It may be reasonable to measure a baseline CK in patients with increased risk for adverse muscle events, including: 1
- Personal or family history of statin intolerance or muscle disease
- Clinical presentation that may increase likelihood of myopathy
- Concomitant drug therapy that may increase risk of myopathy
CK-MB remains useful in specific clinical situations: 1
- Diagnosis of early infarct extension (reinfarction) due to CK-MB's shorter half-life compared to troponin
- Evaluation of periprocedural myocardial injury during cardiac interventions
Interpretation of CK Results
- The threshold for concerning CK elevation is typically 10 times above the upper limit of normal 2
- Serial testing may be more effective than single measurements in detecting mild increases in CK, with reference change values of about +140% and -60% being significant 3
- For patients with suspected myocardial infarction, troponin is the preferred biomarker due to its superior cardiac specificity 1
Monitoring Recommendations When CK is Elevated
- For patients with elevated CK related to medications, consider monitoring CK levels every 4 weeks until normalized 2
- In patients with muscle symptoms and elevated CK, temporary discontinuation of the offending medication (e.g., statins) should be considered 2
- For severe CK elevation (>10× ULN) or signs of rhabdomyolysis, immediate discontinuation of the offending medication is advised 2
Potential Pitfalls
- CK levels can be elevated due to many non-pathological factors including exercise, ethnicity, and gender, leading to false positives 3
- The clinical significance of detecting minor CK elevations must be weighed against potential unnecessary testing and patient anxiety 4
- In patients with possible substance-use conditions, CK may continue to trend up even after six hours from presentation and begin to decrease after 42 hours, making interpretation challenging 4
In conclusion, unless there are specific clinical indications such as muscle symptoms, personal/family history of muscle disorders, or specific cardiac scenarios, routine CK testing is not recommended and adds little value to clinical decision-making 1.