title: Combining C-reactive protein and interleukin-6 may be useful to detect periprosthetic hip infection.
abstract: BACKGROUND
  The sensitivity and specificity to detect periprosthetic infection of the different methods have been questioned, and no single laboratory test accurately detects infection before revision arthroplasty.
  
  
  OBJECTIVE
  We asked whether preoperative C-reactive protein (CRP) and interleukin-6 (IL-6) could lead to similar sensitivity, specificity, and predictive values as our previous results obtained with intraoperative frozen section (FS) in revision total hip arthroplasty (THA).
  
  
  METHODS
  We prospectively followed 69 patients who had undergone revision THA for failure of a primary THA. The definitive diagnosis of an infection was determined on the basis of positive histopathologic evidence of infection or growth of bacteria on culture.
  
  
  RESULTS
  Eleven of the 69 hips were infected. The combination of an elevated CRP and IL-6 was correlated with deep infection in all the cases and showed a sensitivity of 0.57 (0.13-1.00), a specificity of 1.00 (0.99-1.00), a positive predictive value of 1.00 (0.87-1.00), and a negative predictive value of 0.94 (0.87-1.00). FS showed a sensitivity of 0.81 (0.54-1.00), a specificity of 0.98 (0.94-1.00), a positive predictive value of 0.90 (0.66-1.00), and a negative predictive value of 0.96 (0.91-1.00). Combining CRP and IL-6 provided similar sensitivity, specificity, and positive predictive values as the FSs.
  
  
  CONCLUSIONS
  Our data suggest the combination of CRP and IL-6 would be a useful serologic tool to complement others when diagnosing periprosthetic infection.
authors.affiliation: Hip Surgery Unit, Institute of Orthopaedics Carlos E. Ottolenghi, Italian Hospital of Buenos Aires, Potosí 4215 (C1199ACK), Buenos Aires, Argentina. martin.buttaro@hospitalitaliano.org.ar
authors.forename: Martin A
authors.initials: MA
authors.lastname: Buttaro
authors.forename: Ignacio
authors.initials: I
authors.lastname: Tanoira
authors.forename: Fernando
authors.initials: F
authors.lastname: Comba
authors.forename: Francisco
authors.initials: F
authors.lastname: Piccaluga
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001118:Argentina; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis*; D005260:Female; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016459:Prosthesis-Related Infections / Q000175:diagnosis* / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D012086:Reoperation; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; C508600:IL6 protein, human; D015850:Interleukin-6; D002097:C-Reactive Protein