title: The use of receiver operating characteristics analysis in determining erythrocyte sedimentation rate and C-reactive protein levels in diagnosing periprosthetic infection prior to revision total hip arthroplasty.
abstract: BACKGROUND
  Periprosthetic infection (PPI) is a difficult complication in total joint arthroplasty, and while erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are acute phase reactants thought to be of high predictive value for diagnosing infection, no clear cut-off values have been defined. The current study aimed to determine the cut-off values for ESR and CRP that improve clinical differentiation between aseptic failure and PPI in total hip arthroplasty (THA).
  
  
  METHODS
  Four hundred and seventy-nine patients who underwent revision THA for either aseptic mechanical failure or PPI during the period of 2000 to 2005 were included in the study. Specific exclusion criteria were applied to eliminate inflammatory or other confounding conditions. All patients underwent preoperative testing of ESR and CRP. Receiver operating characteristic (ROC) curves were constructed to determine maximum sensitivity and specificity.
  
  
  RESULTS
  Patients with PPI had significantly higher ESR and CRP values compared to patients undergoing revision for aseptic etiologies. An ESR threshold of 30 mm/h gave a sensitivity of 94.3% and a CRP threshold of 10 mg/l gave a sensitivity of 91.1%. Combining both ESR and CRP cut-offs for a positive diagnosis increased the sensitivity to 97.6%. However, when calculated by ROC analysis, the predictive cut-offs equated to 31 mm/h for ESR and 20.5 mg/l for CRP.
  
  
  CONCLUSIONS
  The gold standard for diagnosing PPI remains bacterial culture, but sensitivity is negatively affected by prior antibiotic exposure, strongly adherent bacteria, slow growing persisters, and biofilms. ESR and CRP are reflective of systemic changes in infection and pose an attractive, less invasive alternative with reasonable sensitivity and specificity. The current study is the first to identify ideal cut-off values for ESR and CRP in THA patients, providing an optimum balance between sensitivity and specificity based on ROC curves.
authors.affiliation: The Rothman Institute of Orthopedics, Thomas Jefferson University, 925 Chestnut Street, Philadelphia, PA 19107, USA.
authors.forename: Elie
authors.initials: E
authors.lastname: Ghanem
authors.forename: Valentin
authors.initials: V
authors.lastname: Antoci
authors.forename: Luis
authors.initials: L
authors.lastname: Pulido
authors.forename: Ashish
authors.initials: A
authors.lastname: Joshi
authors.forename: William
authors.initials: W
authors.lastname: Hozack
authors.forename: Javad
authors.initials: J
authors.lastname: Parvizi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000032:analysis*; D005260:Female; D006622:Hip Prosthesis / Q000382:microbiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D016459:Prosthesis-Related Infections / Q000175:diagnosis*; D012372:ROC Curve; D012015:Reference Standards; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D002097:C-Reactive Protein