What are the clinical predictors and diagnostic eliminators for Legionnaires disease?

Updated: Aug 24, 2018
  • Author: Burke A Cunha, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

A clinical point score, as shown in the table below, may be helpful in increasing the probability of correctly diagnosing LD and prompting specific/definitive LD testing.

Table 1. Legionnaires Disease: Six Clinical Predictors and Diagnostic Eliminators in Adults Admitted with Pneumonia a (Open Table in a new window)

Diagnostic Predictors

Diagnostic Eliminators

Clinical Predictors

  • Fever (>102°F)

Clinical Eliminators

  • Sore throat
  • Severe myalgias

Laboratory Predictors b

  • Highly elevated ESR (>90 mm/h) or CRP (>180 mg/L)
  • Highly elevated ferritin levels (>2 X normal)
  • Hypophosphatemia (on admission/early)
  • Highly elevated CPK (>2 X normal)
  • Microscopic hematuria (on admission)

Laboratory Eliminators

  • Leukopenia
  • Thrombocytopenia
  • Negative chest radiographic findings (no infiltrates)

Legionnaire disease very likely if >3 predictors present

Legionnaires disease very unlikely if 3 diagnostic eliminators present

Abbreviations: CPK = creatinine phosphokinase test; CRP = C-reactive protein; ESR = erythrosedimentation rate.

a Pulmonary symptoms: shortness of breath, cough, and so forth with fever and a new focal/segmental infiltrate on chest radiograph.

b Otherwise unexplained. If finding is due to an existing disorder, it should not be used as a clinical predictor.


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