title: Poor utility of serum interleukin-6 levels to predict indolent periprosthetic shoulder infections.
abstract: BACKGROUND
  Infection after shoulder arthroplasty can present a diagnostic challenge. The purpose of this study was to evaluate the utility of serum interleukin-6 (IL-6) levels in diagnosis of periprosthetic infection in patients undergoing revision shoulder arthroplasty.
  
  
  METHODS
  We prospectively enrolled 69 patients who underwent revision shoulder arthroplasty at one institution. All patients underwent a standard preoperative and intraoperative workup for infection, which included shoulder aspirate culture, erythrocyte sedimentation rate, C-reactive protein level, tissue culture, and frozen section analysis. In addition, serum levels of IL-6 were measured preoperatively in all patients. Infection classification was divided into 4 groups, (1) definite, (2) probable, (3) possible, and (4) no infection, on the basis of previously reported criteria using intraoperative cultures and preoperative and intraoperative findings of infections.
  
  
  RESULTS
  Of the 69 patients, 24 were classified as having a definite or probable infection. Propionibacterium acnes was the offending organism for the majority of these cases (20 of 24, 83%). IL-6 was not a sensitive marker of infection for these patients (sensitivity: 3 of 24, 12%; specificity: 3 of 45, 93%). The sensitivity of serum IL-6 was lower compared with erythrocyte sedimentation rate (sensitivity: 10 of 24, 42%; specificity: 37 of 45, 82%) and C-reactive protein level (sensitivity: 11 of 24, 46%; specificity: 42 of 45, 93%). For the non-P. acnes cases (1 Staphylococcus aureus, 1 Enterobacter cloacae, 2 coagulase-negative Staphylococcus species), the sensitivity of IL-6 was 25% (1 of 4).
  
  
  CONCLUSIONS
  Serum IL-6 is not an effective marker for diagnosis of infection in shoulder arthroplasty. On the basis of this large prospective study, we do not recommend its use as a preoperative diagnostic test in patients undergoing revision shoulder arthroplasty.
authors.affiliation: Department of Orthopedic Surgery, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Grosso
authors.affiliation: Department of Orthopedic Surgery, The Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: Salvatore J
authors.initials: SJ
authors.lastname: Frangiamore
authors.affiliation: Department of Orthopedic Surgery, The Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: Anas
authors.initials: A
authors.lastname: Saleh
authors.affiliation: Department of Orthopedic Surgery, The Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: Mario Farias
authors.initials: MF
authors.lastname: Kovac
authors.affiliation: Department of Anatomic Pathology, The Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: Riku
authors.initials: R
authors.lastname: Hayashi
authors.affiliation: Department of Orthopedic Surgery, The Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: Eric T
authors.initials: ET
authors.lastname: Ricchetti
authors.affiliation: Department of Anatomic Pathology, The Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Bauer
authors.affiliation: Department of Orthopedic Surgery, The Cleveland Clinic Foundation, Cleveland, OH, USA. Electronic address: Iannotj@ccf.org.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Iannotti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019643:Arthroplasty, Replacement / Q000009:adverse effects*; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016459:Prosthesis-Related Infections / Q000097:blood* / Q000175:diagnosis* / Q000382:microbiology; D012086:Reoperation; D012785:Shoulder Joint / Q000382:microbiology / Q000601:surgery
chemical_list: D015415:Biomarkers; D015850:Interleukin-6
keywords: Propionibacterium acnes; Shoulder arthroplasty; inflammatory markers; interleukin-6; periprosthetic infection; revision shoulder arthroplasty