Creatine kinase (CK), Creatine phosphokinase (CPK)

Sample
- 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.
Precautions
- 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.
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 onset of infarction.
- This enzyme is also used to determine the effectiveness of thrombolytic therapy used for myocardial infarction.
Pathophysiology
- 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 (CK) is found predominantly in the heart muscles and Skeletal muscles.
- Low concentration is seen in the brain.
- CK level rises within 6 hours after the injury.
- If the injury is transient, then the peak level is 18 hours and then returns to normal in 2 to 3 days.
- Isoenzymes of CPK are:
- CK-BB = CK 1 = This is the fast moving component.
- This is found mainly in the Brain and the lesser amount found in the urinary bladder, stomach, and prostate.
- These enzymes are present in the cytosol and myofibrillar structure of the cells.
- 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 muscle.
- Skeletal muscle is 99% MM, and cardiac is 70%.
- CK-BB = CK 1 = This is the fast moving component.
- CK activity in the serum depends upon various physiologic variants like muscle mass.
- It is lower in the female as a comparison to male.
- Depends on the ethnic group like more in black American female than white males.
- CK-MB is raised in the myocardial infarction.
- It does not arise in the case of angina, congestive heart failure, and pulmonary embolism.
- The mild rise may be seen in unstable angina, and it may indicate 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, 24 hours of admission reflect the timing, quantity, and resolution of myocardial infarction.
-
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 the healthy person.
- CK-MM depends on the muscle mass; large muscular people may have a high normal range.
Clinical significance
- This greatly elevated in muscular diseases, especially muscular dystrophy (Duchenne type), where it is 50 times the upper normal 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, haves 3 to 6 times raised theCK levelK in their blood.
- 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.
- Myocardial infarction
- CK-MB is normal initially in MI and begins to rise:
- After 2 to 4 hours after the infarction.
- The peak 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, then it is clear that the patient had no MI attack.
- The CK-MB level is helpful to quantify 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).
- CK-MB is normal initially in MI and begins to rise:
- Liver diseases
- 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 main increase in CK-3 (CK-MM).
- There is no CK-1 (CK-BB) increase.
- Thyroid diseases
- In hypothyroid 60% of the cases, there is 5 to 50 times 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).
Normal
Source 1
- 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).
- Isoenzymes:
- CK-MM (CK-3) =94 to 100 %
- CK-MB (CK-2)= 0 to 6 %
- CK-BB (CK-1) = 0 %
Source 2
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 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.
- Hypothyroidism.
- 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.
- Myocarditis.
- cardiac ischemia.
- ventricular arrhythmias
Raised level of CK-MM:
- Muscular dystrophy.
- Rhabdomyolysis.
- Myositis.
- Recent injury.
- Intramuscular injection.
- Trauma and crushing injuries.
- Hypothyroidism.
- shock.
Raised level of CK-BB:
- Brain Injury.
- Brain cancers.
- Cerebrovascular accidents.
- Subarachnoid hemorrhage.
- Shock.
- Seizure.
- Adenocarcinoma, especially lung and breast.
- Pulmonary infarction.
- Normal values are found in myasthenia gravis and multiple sclerosis.