title: Analysis of synovial inflammatory markers to differ infectious from gouty arthritis.
abstract: OBJECTIVE
  Septic and gouty arthritis show the same clinical symptoms, but septic arthritis is an orthopedic emergency and needs immediate surgical intervention, whereas a systemic drug therapy is needed in acute gouty arthritis. The aim of this study was to investigate which inflammatory markers allow an accurate differentiation of septic and gouty arthritis.
  
  
  METHODS
  This was a retrospective examination of serum markers (peripheral white blood cells, C-reactive Protein and uric acid) and inflammatory markers in the synovial fluid (lactate, glucose, uric acid, lactate dehydrogenase, synovial fluid white blood cell count, total protein, and interleukin-6) in 53 patients with culture-verified septic arthritis and 29 with gouty arthritis. Receiver-Operating-Characteristic-curves with corresponding Area under the curve (AUC), sensitivity, specificity, likelihood-ratio and interval likelihood-ratios were calculated to define the diagnostic potential of the inflammatory markers.
  
  
  RESULTS
  Synovial lactate showed the greatest diagnostic potential (AUC = 0.901, sensitivity = 89.5%, specificity = 77.3%, negative likelihood-ratio = 0.14) followed by synovial glucose (AUC=0.853) and synovial uric acid (AUC = 0.841).
  
  
  CONCLUSIONS
  Lactate in the synovial fluid has excellent diagnostic potential to differ septic arthritis from gouty arthritis. Synovial lactate levels above 10 mmol/L almost proofed septic arthritis, lactate levels lower than 4.3 mmol/L make it very unlikely.
authors.affiliation: Department of Trauma Surgery and Orthopedics, Hospital of Dachau, Academic Teaching Hospital of the Ludwig-Maximilians-University of Munich, Krankenhausstraße 15, 85221 Dachau, Germany; Technical University of Munich, Faculty of Medicine, Ismaninger Straße 22, 81675 Munich, Germany. Electronic address: markus.1.lenski@googlemail.com.
authors.forename: Markus
authors.initials: M
authors.lastname: Lenski
authors.affiliation: Department of Trauma Surgery and Orthopedics, Hospital of Dachau, Academic Teaching Hospital of the Ludwig-Maximilians-University of Munich, Krankenhausstraße 15, 85221 Dachau, Germany. Electronic address: Michael.Scherer@amperkliniken.de.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Scherer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015210:Arthritis, Gouty / Q000175:diagnosis* / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007239:Infections / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013582:Synovial Fluid / Q000378:metabolism*
chemical_list: D015415:Biomarkers
keywords: Gouty arthritis; Inflammatory marker; Interleukin-6; Lactic acid; Septic arthritis; Synovial fluid