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Sample

  1. It is done on serum (clotted blood 3-5 ml).
    1. The plasma may also be used.
  2. The sample is stable 4 to 8 hours at room temperature.
    1. 1 to 2 days stable at  4 °C. (in another reference the stability at 4 °C for 8 to 12 hours).
  3. One month stable at -20 °C.

Precautions

  1. Avoid excessive physical therapy.
  2. There is no needed for special preparation of the patient.
  3. Avoid the hemolyzed sample. 
  4. Citrate and fluoride inhibit the CK activity.
  5. Protect from light.
  6. Store in airtight tubes.

Purpose of the test

  1. To find cardiac muscular injury (myocardial infarction).
  2. To support the possibility of neurologic or skeletal muscle diseases (Muscular dystrophy).
  3. This test is specific for the muscular and cardiac muscle injury.

Pathophysiology

  1. CPK (creatine phosphate) is the incorrect name and actually, this is Creatine kinase.
    1. CK gives reversible phosphorylation reaction.

  1. Creatine Kinase (CK) is found predominantly in the heart muscles and Skeletal muscles.
  2. Low concentration is seen in the brain.
  3. Ck level rises within 6 hours after the injury.
  4. If the injury is transient then peak level is at 18 hours and then return to normal in 2 to 3 days.
  5. Isoenzymes of CPK are:
    1. CK-MM = This is found in the  Skeletal and cardiac muscle. Skeletal muscle is 99% MM and cardiac is 70%.
    2. CK-MB =This is found in cardiac and skeletal muscles. Cardiac muscle has 30% and skeletal muscle has 1% MB.
    3. CK-BB = This is found mainly in the Brain and the lesser amount found in urinary bladder, stomach, and prostate.
      1. These enzymes are present in the cytosol and myofibrillar structure of the cells.

  1. CK activity in the serum depends upon various physiologic variants like muscle mass.
    1. It is lower in the female as a comparison to male.
    2. Depends on the ethnic group like more in black American female than white males. 
  2. CK-MM is raised in the muscular injury.
  3. CK-MB is raised in the myocardial infarction.
  4. CK-BB is raised in the brain injury (also in the lung injury).
  5. CK-MB level does not rise in angina, pulmonary embolism, or congestive heart failure.

Clinical significance

  1. This greatly elevated in the muscular diseases, especially muscular dystrophy (Duchenne type) where it is 50 times of the upper normal limit.
    1. This may be raised before the clinical disease is apparent.
    2. CK activity decreases with the increasing age of the patient.
    3. Patient with Duchenne disease carriers female, 50 to 80%  has 3 to 6 times raised the level of CK in their blood.
    4. Markedly raised level of CK is seen viral myositis, polymyositis, and muscle diseases.
    5. The level is normal in the neurogenic muscular diseases like myasthenia gravis, multiple sclerosis, poliomyelitis, and Parkinson disease.
      1. CK-MM is 7 to 12 times increased than normal value.
  2. Myocardial infarction
    1. CK-MB is normal initially in MI and begins to rise:
      1. After 2 to 4 hours after the infarction.
      2. The peak between 12 to 24 hours.
      3. Return to normal within 48 hours.
      4. 10 to 25 times of the normal value.
    2. Nowadays more specific test than CK- MB is Troponin-T.
      • CK-MB is 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.

  1. Liver diseases
    1. As the liver has the negligible amount of CK, so there is no marked increase of CK in liver diseases.
    2. In cirrhosis CK is normal.
  2. Central nervous system diseases 
    1. There is an increase in the CK level in cerebrovascular diseases and with cerebral ischemia.
    2. There is a main increase in the CK-3 (CK-MM).
    3. There is no CK-1 (CK-BB) increase.
  3. Thyroid diseases
    1. In hypothyroid 60% of the cases, there is 5 to 50 times elevation than the normal range.
    2. In hyperthyroidism, the CK activity is low to the lower level of normal.
    3. The main isoenzyme is CK-3 (CK-MM). 

Normal

Source 1

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

Raised level of total CK:

  1. Increased CK / CPK seen in :
    1. Acute myocardial infarction.
    2. Severe myocarditis.
    3. After open heart surgery.
    4. Acute cerebrovascular accidents.
    5. Progressive muscular dystrophy.
    6. Dermatomyositis and Polymyositis.
    7. Electric shock.
    8. Malignant hyperthermia.
    9. Reye's syndrome.
    10. Last week of pregnancy and during childbirth.
    11. Hypothyroidism.
    12. Acute psychosis.
    13. Neoplasm of the prostate, GI Tract, and Urinary bladder.

CK is increased in:

  1. The only raised level of CK is seen in the injury of heart muscles, skeletal muscles, and brain.
    1. CK-MM is raised in muscular injuries.
    2. CK-MB is raised in myocardial infarction of damage.
    3. CK-BB is raised in brain injury.

Raised level of CK-MB:

  1. Acute myocardial infarction.
  2. Cardiac surgery ( e.g an aneurysm ).
  3. cardiac defibrillation.
  4. Myocarditis.
  5. cardiac ischemia.
  6. ventricular arrhythmias

Raised level of CK-MM:

  1. Muscular dystrophy.
  2. Rhabdomyolysis.
  3. Myositis.
  4. Recent injury.
  5. Intramuscular injection.
  6. Trauma and crushing injuries.
  7. Hypothyroidism.
  8. shock.

Raised level of CK-BB:

  1. Brain Injury.
  2. Brain cancers.
  3. Cerebrovascular accidents.
  4. Subarachnoid hemorrhage.
  5. Shock.
  6. Seizure.
  7. Adenocarcinoma especially lung and breast.
  8. Pulmonary infarction.

 


Possible References Used

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