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Eosinopenia to differentiate crystal-induced and septic arthritis
  1. Agathe Vigouroux1,
  2. Agnes Ostertag2,
  3. Anne-Claude Crémieux3,4,
  4. Thomas Bardin1,2,
  5. Augustin Latourte1,2,
  6. Hang-Korng Ea1,2,
  7. Pascal Richette1,2
  1. 1Service de Rhumatologie, AP-HP, Hôpital Lariboisière, Paris, France
  2. 2Université de Paris, INSERM, UMR-S 1132 BIOSCAR, Paris, France
  3. 3Infectiology Department, Hopital Saint-Louis, Paris, France
  4. 4Université de Paris, FHU PROTHEE, Paris, France
  1. Correspondence to Professor Pascal Richette, Service de Rhumatologie, AP-HP, Hopital Lariboisière, Paris, Île-de-France, France; pascal.richette{at}

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Septic and crystal-induced arthritis (related to calcium pyrophosphate deposition disease or gout) are the two main causes of acute knee arthritis. The features of septic and crystal-induced arthritis are very similar, with a high level of acute pain, sharp inflammatory syndrome and occasionally fever, so the differential diagnosis is difficult.1 2

Pyogenic septic arthritis of the knees is associated with high mortality and morbidity and is considered a medical emergency.3 In case of severe sepsis, probabilistic antibiotic therapy and close monitoring are recommended.4 Gram staining and culture of synovial fluid (SF) are the gold standard for the diagnosis of septic arthritis, but identifying the bacterium often takes several days. Examining SF for the identification of crystals allows for a definite diagnosis of gout and CPP crystal arthritis but requires skills and facilities that are not always present in the primary care setting or in emergency departments. …

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  • Handling editor Josef S Smolen

  • Twitter @A_Latourte

  • Contributors AV collected the data. PR and AV designed the study and wrote the manuscript. AO performed the statistical analysis. A-CC, TB, AL and H-KE improved the final draft

  • Funding This study was funded by "ART Viggo".

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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