title: Measurement of serum C-reactive protein concentration for discriminating between suppurative arthritis and osteoarthritis in dogs.
abstract: BACKGROUND
  In a dog with joint pain, it is important to determine whether it has suppurative joint disease, characterized by exudation of neutrophils in the synovial fluid, or not, as this affects choice of diagnostic tests and treatments. The aim of this study was to evaluate whether measurement of serum C-reactive protein (CRP) concentration could be used to discriminate between dogs with suppurative arthritis and osteoarthritis (OA). Furthermore, the concentrations of serum and synovial fluid interleukin (IL) 6 concentrations were measured in dogs with joint disease and in healthy dogs, and were correlated to serum CRP concentrations.
  
  
  METHODS
  Dogs with joint pain were enrolled prospectively and were classified to have suppurative arthritis or OA based on synovial fluid analysis and radiographic/arthroscopic findings. Healthy Beagles were enrolled as a comparative group. CRP and IL-6 concentrations were measured with canine-specific immunoassays. The performance of CRP concentration in discriminating between dogs with suppurative arthritis and OA was evaluated using a previously established clinical decision limit for CRP (20 mg/l), and by receiver operator characteristic (ROC) curve and logistic regression analysis. Comparisons of CRP and IL-6 concentrations between groups were performed using t-tests, and correlations by Spearman rank correlation coefficients.
  
  
  RESULTS
  Samples were obtained from 31 dogs with suppurative arthritis, 34 dogs with OA, and 17 healthy dogs. Sixty-two out of 65 dogs with joint disease were correctly classified using the clinical decision limit for CRP. Evaluation of ROC curve and regression analysis indicated that serum CRP concentrations could discriminate between suppurative arthritis and OA. Dogs with suppurative arthritis had higher serum CRP and serum and synovial fluid IL-6 concentrations compared to dogs with OA (p < 0.001). Dogs with OA had higher synovial fluid IL-6 concentrations (p < 0.001), but not higher serum CRP (p = 0.29) or serum IL-6 (p = 0.07) concentrations, compared to healthy dogs. There was a positive correlation between synovial fluid IL-6 and serum CRP concentrations (rs= 0.733, p < 0.001), and between serum IL-6 and serum CRP concentrations (rs= 0.729, p < 0.001).
  
  
  CONCLUSIONS
  CRP concentration was found to discriminate well between dogs with suppurative arthritis and OA.
authors: Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden. anna.hillstrom@slu.se.
authors: Anna
authors: A
authors: Hillström
authors: Evidensia Södra Djursjukhuset, Stockholm, Sweden.
authors: Jonas
authors: J
authors: Bylin
authors: Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors: Ragnvi
authors: R
authors: Hagman
authors: Department of Translational Sciences, RIA IMed, AstraZeneca R&D Mölndal, Mölndal, Sweden.
authors: Karin
authors: K
authors: Björhall
authors: Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors: Harold
authors: H
authors: Tvedten
authors: Safety Assessment, AstraZeneca R&D Södertälje, Södertälje, Sweden.
authors: Kristian
authors: K
authors: Königsson
authors: Department of Medical Sciences, Molecular Epidemiology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors: Tove
authors: T
authors: Fall
authors: Translational Haemophilia Pharmacology, Novo Nordisk, Maaloev, Denmark.
authors: Mads
authors: M
authors: Kjelgaard-Hansen
mesh_terms: D000818:Animals; D001170:Arthritis, Infectious / Q000097:blood / Q000662:veterinary*; D002097:C-Reactive Protein / Q000378:metabolism*; D003937:Diagnosis, Differential; D004283:Dog Diseases / Q000097:blood / Q000175:diagnosis*; D004285:Dogs; D005260:Female; D008297:Male; D010003:Osteoarthritis / Q000097:blood / Q000662:veterinary*; D011446:Prospective Studies; D013582:Synovial Fluid / Q000378:metabolism
chemical_list: D002097:C-Reactive Protein
keywords: C-reactive protein; Immune-mediated arthritis; Interleukin 6; Osteoarthritis; Septic arthritis; Suppurative arthritis; Synovial fluid