Blood biochemistry: creatine phosphokinase

• Occurs as 3 isoenzymes in skeletal muscle, cardiac muscle and central nervous system (CNS):
  • CK1 (BB) in brain, peripheral nerve, cerebrospinal fluid and viscera. Not found in serum.
  • CK2 (MB) in cardiac muscle, with very small amounts in skeletal muscle.
  • CK3 (MM) in skeletal and cardiac muscle.
• Most sensitive indicator of muscle damage.
• Half-life 2-4 h.
• Levels peak 6-12 h post-injury, returning to normal in 2-3 days after cessation of injury.
• Persistent elevation indicates continuing or active disease.

Uses

Alone

• Skeletal muscle injury.

In combination

• With AST Blood biochemistry: aspartate aminotransferase and LDH Blood biochemistry: lactate dehydrogenase to aid distinction between hepatic and muscle sources of AST and LDH.

Other points

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