What workup or tests should be completed in cellulitis diagnosis?

Updated: Jun 14, 2019
  • Author: Thomas E Herchline, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Generally, no workup is required in uncomplicated cases of cellulitis that meet the following criteria:

  • Limited area of involvement

  • Minimal pain

  • No systemic signs of illness (eg, fever, altered mental status, tachypnea, tachycardia, hypotension)

  • No risk factors for serious illness (eg, extremes of age, general debility, immunocompromise)

The Infectious Disease Society of America (IDSA) recommends the following blood tests for patients with soft-tissue infection who have signs and symptoms of systemic toxicity [2] :

  • Blood cultures

  • CBC with differential

  • levels of creatinine, bicarbonate, creatine phosphokinase, and C-reactive protein (CRP)

Blood cultures should also be done in the following circumstances [2] :

  • Moderate to severe disease [2] (eg, cellulitis complicating lymphedema [3] )

  • Cellulitis of specific anatomic sites (eg, facial and especially ocular areas)

  • Patients with a history of contact with potentially contaminated water [4]

  • Patients with malignancy who are receiving chemotherapy

  • Neutropenia or severe cell-mediated immunodeficiency

  • Animal bites

Other tests to consider are as follows:

  • Mycologic investigations are advisable if recurrent episodes of cellulitis are suspected to be secondary to tinea pedis or onychomycosis

  • Creatinine levels help assess baseline renal function and guide antimicrobial dosing

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