Is a creatine phosphokinase (CPK) level of 68 considered normal in a patient with anemia of inflammation and anemia of chronic disease?

Normal Creatine Phosphokinase Level in Anemia of Inflammation and Chronic Disease

A creatine phosphokinase (CPK) level of 68 is considered normal in a patient with anemia of inflammation and anemia of chronic disease. This value falls within the typical normal reference range for CPK, which is not typically affected by these types of anemia.

Understanding CPK and Anemia

CPK Levels in Inflammatory Conditions

• CPK is an enzyme found primarily in the heart, brain, and skeletal muscle
• Normal CPK levels typically range from approximately 30-200 U/L (though reference ranges may vary slightly between laboratories)
• The value of 68 falls well within this normal range
• Unlike some other laboratory parameters, CPK is not characteristically elevated in anemia of inflammation or anemia of chronic disease unless there is concurrent muscle damage

Anemia of Inflammation/Chronic Disease

Anemia of inflammation (AI), also known as anemia of chronic disease (ACD), is characterized by:

• Inflammatory cytokine-mediated changes in iron metabolism 1
• Increased production of hepcidin, which blocks iron release from macrophages, hepatocytes, and enterocytes 2
• Shortened erythrocyte half-life and blunted erythropoietin response 3
• Laboratory findings typically include:
  • Low serum iron
  • Low to normal transferrin
  • High to normal serum ferritin
  • Normal CPK levels

Diagnostic Considerations

Differentiating Types of Anemia

According to the European Consensus on diagnosis and management of iron deficiency and anemia in inflammatory bowel diseases 4, the diagnostic criteria for anemia types include:

• Iron deficiency anemia: Serum ferritin <30 μg/L in the absence of inflammation
• Anemia of chronic disease: Serum ferritin >100 μg/L and transferrin saturation <20% in the presence of inflammation
• Mixed anemia: Serum ferritin between 30-100 μg/L in the presence of inflammation

CPK levels are not part of these diagnostic criteria and would not be expected to be abnormal in these conditions.

When to Consider Elevated CPK

CPK would only be elevated in a patient with anemia of inflammation if there was concurrent:

• Muscle injury or inflammation (myositis)
• Cardiac injury
• Recent seizure activity
• Certain medications that can cause muscle damage

For example, in sarcoidosis with inflammatory myopathy, CPK can be markedly elevated 5, but this is due to the muscle involvement rather than the anemia itself.

Clinical Implications

Normal CPK in Context

• A normal CPK level of 68 is expected and reassuring in a patient with anemia of inflammation/chronic disease
• This finding suggests absence of concurrent muscle or cardiac damage
• Focus should remain on managing the underlying anemia and its causes

Management Focus

According to guidelines 4, management should focus on:

• Treating the underlying inflammatory condition
• Iron supplementation if iron deficiency is present
• Intravenous iron for patients with clinically active inflammatory disease
• Erythropoiesis-stimulating agents in selected cases with insufficient response to iron therapy

Key Takeaways

• CPK level of 68 is normal and expected in anemia of inflammation/chronic disease
• This laboratory value does not require further investigation or intervention
• Management should focus on the underlying anemia and its causes rather than the normal CPK value
• If muscle symptoms were present despite normal CPK, further evaluation might be warranted, but based on the information provided, this value is reassuringly normal