Creatine Kinase (CK), Total, Serum

CPT Test code: 82550

Specimen:	Serum (preferred) or plasma
Volume:	2 mL
Minimum Volume:	0.4 mL
Container:	Red-top tube, gel-barrier tube, or green-top (heparin) tube
Special Instructions:	State patient’s sex on the request form.
Collection:	Separate serum or plasma from cells. Avoid prolonged contact of serum or plasma with red cells.
Storage Instructions:	Maintain specimen at room temperature.
Patient Preparation:	Avoid exercise before venipuncture. Increases may be anticipated in the immediate postoperative period following surgical procedures involving incision through muscle.
Causes for Rejection:	Hemolysis
Use:	Test for acute myocardial infarct and for skeletal muscular damage; elevated in some patients with myxedema (hypothyroidism), malignant hyperthermia syndrome, and muscular dystrophy. CK is a marker for Duchenne muscular dystrophy, with elevations of 20 to 200 times normal.¹ CK is increased in female carriers of this X-linked disease, and in muscular stress, in polymyositis, dermatomyositis, and with muscle trauma. Elevated in myocarditis. Documentation of postictal state (recent grand mal seizure). Extremely high values are seen in some instances of myositis and in the postictal state. CK may be elevated in a number of entities, including the eosinophilia-myalgia syndrome.² Marked increases occur with rhabdomyolysis including that with cocaine intoxication.³ CK is sometimes increased with cerebrovascular accident. Malignancy (advanced) may show increased CK.⁴ Cardioversion with multiple shocks may release CK-MB and may result in a false-positive diagnosis of myocardial infarction.⁵ Low CK may reflect decreased muscle mass. It has been reported with a number of entities, including metastatic neoplasia, patients with steroid therapy, with alcoholic liver disease⁶ and with connective tissue diseases.⁷ Overnight bedrest may lower CK 10% to 20%.
Limitations:	Intramuscular injections increase serum CK activity. Elevated following exercise. Normal at onset of acute MI unless the subject has been exercising or doing physical work. Elevation of CK following acute MI may not be observed until six or more hours after onset. CK returns to normal in approximately 48 to 72 hours after acute MI. Total CK can be normal in acute MI, when CK-MB is increased. Low CK does not rule out myositis in patients with the connective tissue diseases.⁷ Decreased with pregnancy.
Additional Information:	High CK is found after trauma, surgery, and exercise; these entities may not be accompanied by elevation of CK-MB. To distinguish myoglobinuria from hemoglobinuria, serum CK and LD may be helpful. CK is normal with uncomplicated hemolysis but LD and LD₁ usually are increased. When myoglobin is released, 40-fold elevation of CK may be anticipated with only moderate increase in serum LD and increased LD₅.⁸
Footnotes:	1. Rosalki SB, “Serum Enzymes in Disease of Skeletal Muscle,” Clin Lab Med, 1989, 9(4):767-81. PubMed 2686911 2. Kilbourne EM, Swygert LA, Philen RM, et al, “Interim Guidance on the Eosinophilia-Myalgia Syndrome,” Ann Intern Med, 1990, 112(2):85-7. PubMed 2153013 3. Roth D, Alarcón FJ, Fernández JA, “Acute Rhabdomyolysis Associated With Cocaine Intoxication,” N Engl J Med, 1988, 319(11):673-7. PubMed 3412385 4. Eng C, Skolnick AE, Come SE, “Elevated Creatine Kinase and Malignancy,” Hosp Pract (Off Ed), 1990, 25(12):123, 126, 129-30. PubMed 2123205 5. O’Neill PG, Faitelson L, Taylor A, et al, “Time Course of Creatine Kinase Release After Termination of Sustained Ventricular Dysrhythmias,” Am Heart J, 1991, 122(3 Pt 1):709-14. PubMed 1877446 6. Nanji AA, Blank D, “Low Serum Creatine Kinase Activity in Patients With Alcoholic Liver Disease,” Clin Chem 1981, 27(11):1954. PubMed 7296863 7. Wei N, Pavlidis N, Tsokos G, et al, “Clinical Significance of Low Creatine Phosphokinase Values in Patients With Connective Tissue Diseases,” JAMA, 1981, 246(17):1921-3. PubMed 7288967 8. Faulkner WR, “Update on Myoglobinurias,” Lab Report for Physicians, 1989, 11:91-2.