Is creatine kinase (CK) elevated in pneumonia?

Creatine Kinase Elevation in Pneumonia

Creatine kinase (CK) may be elevated in pneumonia, particularly in cases of severe pneumonia or when caused by specific pathogens such as Mycoplasma pneumoniae, but it is not a standard diagnostic marker for pneumonia. 1

Relationship Between CK and Pneumonia

Evidence from Guidelines

• The British Infection Society and British Thoracic Society guidelines specifically mention that creatine kinase may be elevated in patients with severe myalgia during pneumonia 1
• These guidelines recommend measuring CK "if myositis is suspected" in patients admitted to the hospital with pneumonia, but not as a routine test 1
• CK is not included in the standard diagnostic criteria for pneumonia in any major guidelines 1

Specific Scenarios Where CK Elevation Occurs

1. Severe Pneumonia:

   • In severe cases of pneumonia requiring ICU admission, muscle damage can occur as part of multi-organ dysfunction
   • Patients with septic shock from pneumonia may develop elevated CK due to tissue hypoperfusion 1

2. Pathogen-Specific Associations:

   • Mycoplasma pneumoniae infections have been documented to cause rhabdomyolysis with significantly elevated CK levels 2
   • Viral pneumonias, including parainfluenza and COVID-19, can be associated with elevated CK 3, 4

3. Mechanism of Elevation:

   • CK elevation in pneumonia likely results from:
     • Direct muscle damage from inflammatory cytokines
     • Hypoxia affecting muscle tissue
     • Metabolic derangements in severe illness

Clinical Implications

Diagnostic Value

• CK is not recommended as a standard diagnostic test for pneumonia 1
• Other markers like C-reactive protein (CRP) are more valuable for diagnosing and monitoring pneumonia 1, 5
• The British Thoracic Society guidelines state that CRP is more helpful than CK for diagnosing pneumonia 1

Prognostic Value

• Elevated CK in COVID-19 pneumonia has been associated with poor outcomes (OR 3.01) 4
• When CK elevation occurs in pneumonia, it may indicate more severe disease requiring closer monitoring 1

Recommended Laboratory Testing in Pneumonia

The standard recommended laboratory tests for pneumonia according to guidelines include:

• Complete blood count
• Basic metabolic panel (urea, creatinine, electrolytes)
• Liver function tests
• C-reactive protein (CRP)
• Blood cultures (in hospitalized patients)
• Sputum cultures (in selected cases)
• Procalcitonin (in some cases to guide antibiotic therapy) 1

CK measurement should be considered only when:

• Significant myalgia is present
• Rhabdomyolysis is suspected
• There are signs of muscle involvement 1

Clinical Pearls

• If a patient with pneumonia presents with severe muscle pain, dark urine, or weakness, check CK levels to rule out concomitant rhabdomyolysis
• Markedly elevated CK in a patient with pneumonia may suggest specific pathogens like Mycoplasma or certain viruses
• The absence of CK elevation does not rule out pneumonia, as it is not a sensitive marker for this condition
• Focus on established diagnostic markers like CRP, which has better evidence for use in pneumonia diagnosis and monitoring 1, 5