title: The routine use of atypical cultures in presumed aseptic revisions is unnecessary.
abstract: BACKGROUND
  In presumed aseptic hip and knee revisions, it is common practice to send intraoperative cultures to screen for occult infection. Currently no guidelines exist for the routine use of acid-fast bacillus (AFB) and fungal cultures in this setting.
  
  
  OBJECTIVE
  We established (1) the rate of positive fungal and AFB cultures in aseptic hip and knee revision arthroplasties, (2) factors associated with positive fungal and AFB cultures, (3) the likelihood that positive cultures represent true-positive results, and (4) the hospital charges of sending fungal and AFB cultures routinely.
  
  
  METHODS
  We retrospectively evaluated all 1717 presumed aseptic hip and knee revisions performed from January 2006 to November 2011: 1139 patients had at least one intraoperative fungal culture and 1133 patients had at least one intraoperative AFB culture, with 923 and 920, respectively, achieving 1-year followup. The Musculoskeletal Infection Society criteria were used to classify subsequent infections. We attempted to identify risk factors for positive cultures.
  
  
  RESULTS
  We observed six (0.5%) patients with positive AFB cultures and 19 (1.7%) with positive fungal cultures. Patients undergoing reimplantation procedures were more likely to have a positive fungal culture. The true-positive rate was 0% and 0.1% for AFB and fungal cultures, respectively. The total hospital charges for these cultures over the time frame of our study were USD 1,315,533.
  
  
  CONCLUSIONS
  Given the extremely low rate of true-positive AFB and fungal cultures in presumed aseptic revision joint arthroplasty and the charges associated with maintaining these cultures, we believe their routine use is unwarranted.
  
  
  METHODS
  Level III, prognostic study. See the Instructions for Authors for a complete description of evidence.
authors.affiliation: The Rothman Institute of Orthopedics at Thomas Jefferson University Hospital, 925 Chestnut Street, 5th Floor, Philadelphia, PA, 19107, USA.
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Tokarski
authors.forename: Joseph
authors.initials: J
authors.lastname: O'Neil
authors.forename: Carl A
authors.initials: CA
authors.lastname: Deirmengian
authors.forename: Joseph
authors.initials: J
authors.lastname: Ferguson
authors.forename: Gregory K
authors.initials: GK
authors.lastname: Deirmengian
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D005500:Follow-Up Studies; D006801:Humans; D007432:Intraoperative Period; D016459:Prosthesis-Related Infections / Q000175:diagnosis* / Q000382:microbiology; D012086:Reoperation; D012189:Retrospective Studies; D040141:Staphylococcaceae / Q000302:isolation & purification*