Creatine Kinase (CK), Total

CK is an enzyme that catalyzes the interconversion of ATP and creatine phosphate, controlling energy flow within cells, principally muscle. Its activity is greatest in striated muscle, heart tissue, and brain. The determination of CK activity is a proven tool in the investigation of skeletal muscle disease (muscular dystrophy) and is also useful in the diagnosis of myocardial infarction or stroke.

Normal range:

Male: 49 " “348 IU/L

Female: 38 " “206 IU/L

Use

Marker for injury or diseases of cardiac muscle with good specificity

Measurement of choice for striated muscle disorders

Interpretation

Increased In

Necrosis or inflammation of cardiac muscle: disorders listed under CK-MB (CK index usually >4%)

Necrosis, inflammation, or acute atrophy of striated muscle

Disorders listed under CK-MB (CK index usually <4%)

Muscular dystrophy

Myotonic dystrophy

Amyotrophic lateral sclerosis (>40% of cases)

Polymyositis (70% of cases; average 20 ƒ — ULN)

Thermal and electrical burns (values usually higher than in AMI)

Rhabdomyolysis (especially with trauma and severe exertion); marked increase may be 1,000 times ULN

Severe or prolonged exercise as in marathon running (begins 3 hours after start of exercise; peaks after 8 " “16 hours; usually normal by 48 hours); smaller increases in well-conditioned athletes

Status epilepticus

Parturition and frequently the last few weeks of pregnancy

Malignant hyperthermia

Hypothermia

Familial hypokalemic periodic paralysis

McArdle disease

Drugs and chemicals

Cocaine

Alcohol

Emetine (ipecac) " ”(e.g., bulimia)

Chemical toxicity; benzene ring compounds (e.g., xylene) depolarize the surface membrane and leach out low molecular weight enzymes, producing very high levels of total CK (100% fraction muscle [MM]) with increased LD) (3 " “5 ƒ — normal)

Half of patients with extensive brain infarction. Maximum levels are reached in 3 days; the increase may not appear before 2 days; levels are usually lower than in AMI and remain increased for a longer time; levels return to normal within 14 days; high mortality is associated with levels >300 IU. Elevated serum CK in brain infarction may obscure diagnosis of concomitant AMI.

Some persons with large muscle mass ( ≤2 times normal) (e.g., football players).

Slight increase (occasionally) in

Variable increase after IM injection to two to six times normal level; returns to normal 48 hours after cessation of injections; rarely affects CK-MB, LD-1 (lactate dehydrogenase-1), AST

Muscle spasms or convulsions in children

Healthy African Americans when compared to Caucasian/Hispanic populations

Moderate hemolysis

Decreased In

Decreased muscle mass (e.g., elderly, malnutrition, alcoholism)

RA (about two thirds of patients)

Untreated hyperthyroidism

Cushing disease

Connective tissue disease not associated with decreased physical activity

Pregnancy level (8th " “12th week) is said to be approximately 75% of nonpregnant level

Various drugs (e.g., phenothiazine, prednisone, estrogens, tamoxifen, ethanol), toxins, and insecticides (e.g., aldrin, dieldrin)

Metastatic tumor in the liver

Multiple organ failure

Intensive care patients with severe infection or septicemia

Normal In

Pulmonary infarction

Renal infarction

Liver disease

Biliary obstruction

Some muscle disorders

Thyrotoxicosis myopathy

Steroid myopathy

Muscle atrophy of neurologic origin (e.g., old poliomyelitis, polyneuritis)

Most malignancies

Scleroderma

Acrosclerosis

Discoid lupus erythematosus

Limitations

Following MI, CK activity increases 4 " “8 hours after acute onset, activities peak at 12 " “36 hours, and usually returns to normal activities in 3 " “4 days. Although total CK has been used as a diagnostic tool for MI detection, along with CK-MB, it has been predominantly replaced with troponin I or T due to lack of myocardial specificity.

Exercise and muscle trauma (contact sports, traffic accidents, IM injections, surgery, convulsions, wasp or bee stings, and burns) can elevate serum CK values.

To distinguish myoglobinuria from hemoglobinuria, serum CK and LD may be helpful. CK is normal with uncomplicated hemolysis, but LD and LD-1 usually are increased.