Creatine kinase (CK), Creatine phosphokinase (CPK)
Sample for Creatine kinase
- It is done on serum (clotted blood 3 to 5 ml).
- The plasma may also be used.
- The sample is stable for 4 to 8 hours at room temperature.
- 1 to 2 days stable at 4 °C. (in another reference, the stability at 4 °C for 8 to 12 hours).
- One month stable at -20 °C.
- CK-MB level in case of AMI:
- In the case of AMI, get multiple samples of CK-MB at 6, 12, 18, and 24 hours.
- Some people recommend 4 samples, one immediately, then at 8, 16, and 24 hours.
- While some recommend 3 samples, immediately, 12 hours, and 24 hours.
Precautions for Creatine kinase (CK)
- Avoid excessive physical therapy.
- There is no need for special preparation of the patient.
- Avoid the hemolyzed sample.
- Citrate and fluoride inhibit CK activity.
- Protect from light.
- Store in airtight tubes.
- Please do not take the sample immediately after the I/M injection. Either wait for at least one hour or take the sample before the injection.
- I/M raises the CK level.
- Trauma to the muscles makes the result unreliable for a few days.
Purpose of the test (Indications)
- To find cardiac muscular injury (myocardial infarction).
- To support the possibility of neurologic or skeletal muscle diseases (Muscular dystrophy).
- This test is specific for muscular and cardiac muscle injury.
- CK-MB isoenzymes level helps quantify the degree of myocardial infarction and the timing of the onset of infarction.
- This enzyme is also used to determine the effectiveness of thrombolytic therapy used for myocardial infarction.
Pathophysiology of Creatine kinase (CK)
- CPK (creatine phosphate) is the incorrect name, and actually, this is Creatine kinase.
- CK is also known as Creatine phosphokinase (CPK).
- CK gives a reversible phosphorylation reaction.
Creatine kinase facts sheet:
- Creatine Kinase (CK) is found predominantly in the heart muscles, Skeletal muscles, and brain.
- Concentration in the brain is low.
- It is elevated in 90% to 93% of patients with acute myocardial infarction (AMI).
- In AMI, it behaves like AST (SGOT).
- This is also elevated in myocarditis and some patients with tachyarrhythmias, mostly ventricular type, without any known reason.
- In the case of acute liver cell injury where AST (SGOT) is raised, CK is normal.
- CK level rises within 6 hours after the injury.
- If the injury is transient, the peak level is 18 hours and then returns to normal in 2 to 3 days.
- CK values are usually raised in muscular dystrophy, muscular trauma, and myositis after the surgery, postpartum, and after exercise (moderate to severe).
- This is also raised in delirium, convulsions, and tremens.
- CK level is abnormal after 24 to 48 hours in most persons after heavy drinking of alcohol and in patients with delirium and tremens. But CK level is normal in chronic alcoholics.
- CK level is normal in chronic alcoholics.
- CK level is usually raised after the I/M injections.
- CK level is raised in cases of meningitis, encephalitis, uremic coma, hepatic coma, cerebrovascular accidents, and epilepsy (seizures of epilepsy).
- CK is raised in 19% to 47% of uremia cases.
- CK is raised in about 80% of the cases with hypothyroidism.
- CK is also raised in severe hypokalemia due to changes induced in the skeletal muscles.
Isoenzymes of CPK are:
- CK-BB = CK 1 = This is the fast-moving component.
- This is found mainly in the Brain, and a lesser amount is found in the urinary bladder, stomach, and prostate.
- These enzymes are present in the cells’ cytosol and myofibrillar structure.
- CK-MB = CK 2 = This is found in cardiac and skeletal muscles. The cardiac muscle has 30%, and the skeletal muscle has 1% MB.
- CK-MM = CK 3 = This is found in the Skeletal and cardiac muscles.
- Skeletal muscle is 99% MM, and cardiac is 70%.
- CK activity in the serum depends upon various physiologic variants like muscle mass.
- It is lower in females in comparison to males.
- Depends on the ethnic group, like more black American females than white males.
- CK-MB is raised in myocardial infarction.
- It does not arise in the case of angina, congestive heart failure, or pulmonary embolism.
- The mild rise may be seen in unstable angina, indicating a risk for occlusive attack.
- There may be a rise in shock, myopathies, malignant hyperthermia, or myocarditis.
- A small amount of CK-MB is present in the skeletal muscles, so there may be a mild rise in the injury to skeletal muscles.
- CK-MB level does not rise in angina, pulmonary embolism, or congestive heart failure.
- CK-MB is advised that 12 and 24 hours of admission reflect the myocardial infarction’s timing, quantity, and resolution.
CK and CK-MB level rising pattern:
Enzyme Starts to rise in hours Peak level/hours Returns to normal/days Total CK 4 to 6 24 3 to 4 CK-MB 2 to 4 18 2
- CK-BB is raised in the brain injury (also in the lung injury).
- CK-MM is raised in the muscular injury.
- CK-MM isoenzyme makes up almost all the circulatory total CK in a healthy person.
- CK-MM depends on the muscle mass; large muscular people may have a high normal range.
Clinical significance of creatine kinase
- This is significantly elevated in muscular disorders, especially muscular dystrophy (Duchenne type), where it is 50 times the normal upper limit.
- This may be raised before the clinical disease is apparent.
- CK activity decreases with the increasing age of the patient.
- Patients with Duchenne disease carriers female, 50 to 80, have 3 to 6 times raised CK levels in their blood.
- A markedly raised level of CK is seen in viral myositis, polymyositis, and muscle diseases.
- The level is normal in neurogenic muscular diseases like myasthenia gravis, multiple sclerosis, poliomyelitis, and Parkinson’s disease.
- CK-MM is 7 to 12 times increased than the normal value.
- CK-MB is normal initially in MI and begins to rise:
- 2 to 4 hours after the infarction.
- The peak is between 12 to 24 hours.
- Return to normal within 48 hours.
- 10 to 25 times the normal value.
- Nowadays, a more specific test than CK- MB is Troponin-T.
- CK-MB is a diagnostic of MI.
- If there is negative CK-MB for > 48 hours, it is clear that the patient had no MI attack.
- The CK-MB level is helpful in quantifying the level of muscle damage in MI.
- CK-MB/total CK ratio improves the specificity of CK-MB for myocardial infarction.
- If it is >5% is suggestive of the cardiac source (cardiac muscle damage).
- As the liver has a negligible amount of CK, there is no marked increase of CK in liver diseases.
- In cirrhosis, CK is normal.
Central nervous system diseases:
- There is an increase in the CK level in cerebrovascular diseases and cerebral ischemia.
- There is a noticeable increase in CK-3 (CK-MM).
- There is no CK-1 (CK-BB) increase.
- In hypothyroid 60% of the cases (in another reference, 80%), there is 5 to 50 times more elevation than the normal range.
- In hyperthyroidism, the CK activity is low to the lower level of normal.
The main isoenzyme is CK-3 (CK-MM).
Drawbacks of CK level:
- As CK depends upon muscle mass, its level will be low in a person with less muscle mass.
- CK level after AMI is short when the CK level is raised.
- False raised level after I/M injection.
- 0 to 250 U/L
- Adult male = 55 to 170 units /L
- Female = 30 to 135 units /L
- Above 90 years
- Male = 21 to 203 U/L
- Female = 22 to 99 U/L
- Newborn = 68 to 580 U/L (2 to 3 times of adult value).
- CK-MM (CK-3) =94 to 100 %
- CK-MB (CK-2)= 0 to 6 %
- CK-BB (CK-1) = 0 %
|Age||Male U/L||Female U/L|
|At 37 °C|
|20 to 60 years||52 to 200||35 to 165|
|Adult||38 to 174||26 to 140|
|>90 years||21 to 203||22 to 99|
|AT 30 °C|
|20 to 59 years||25 to 80||20 to 75|
|60 to 69 years||20 to 110||61 to 81|
|70 to 90||22 to 90||19 to 76|
|Adult||15 to 105||10 to 80|
|At 25 °C|
|Adult||10 to 65||7 to 55|
- To convert to SI unit x 0.017 = µKat/L
Raised level of total Creatine kinase (CK):
- Increased CK/CPK seen in:
- Acute myocardial infarction.
- Severe myocarditis.
- After open-heart surgery.
- Acute cerebrovascular accidents.
- Progressive muscular dystrophy.
- Dermatomyositis and Polymyositis.
- Electric shock.
- Malignant hyperthermia.
- Reye’s syndrome.
- Last week of pregnancy and during childbirth.
- Acute psychosis.
- Neoplasm of the prostate, GI Tract, and Urinary bladder.
CK is increased in:
- The only raised level of CK is seen in the injury of the heart muscles, skeletal muscles, and brain.
- CK-MM is raised in muscular injuries.
- CK-MB is raised in myocardial infarction of damage.
- CK-BB is raised in brain injury.
Raised level of CK-MB:
- Acute myocardial infarction.
- Cardiac surgery (e.g., an aneurysm ).
- cardiac defibrillation.
- cardiac ischemia.
- ventricular arrhythmias
Raised level of CK-MM:
- Muscular dystrophy.
- Recent injury.
- Intramuscular injection.
- Trauma and crushing injuries.
Raised level of CK-BB:
- Brain Injury.
- Brain cancers.
- Cerebrovascular accidents.
- Subarachnoid hemorrhage.
- Adenocarcinoma, especially lung and breast.
- Pulmonary infarction.
- Normal values are found in myasthenia gravis and multiple sclerosis.
Questions and answers:
Question 1: What are the types of CK (Creatine phosphokinase)?
There are three types: 1. CK-BB, CK-MM, and CK-MB
Question 2: What is the significance of CK-MB in AMI?
CK-MB rises in first 2 to 4 hours, and peak level is 12 to 24 hours. It returns to normal in 48 hours.