Which lab studies are performed in the evaluation of polymyositis?

Updated: Jan 05, 2021
  • Author: Mythili Seetharaman, MD; Chief Editor: Herbert S Diamond, MD  more...
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The following laboratory findings may be present in polymyositis:

  • Complete blood count (CBC) - May show leukocytosis or thrombocytosis; leukocytosis is present in more than 50% of patients

  • Erythrocyte sedimentation rate or C-reactive protein level - Elevated in 50% of patients with polymyositis

  • Elevated muscle enzyme levels

  • Myoglobinuria

  • Autoantibodies

  • Positive rheumatoid factor  - Found in more than 50% of patients

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