title: The role of intraoperative gram stain in the diagnosis of infection during revision total hip arthroplasty.
abstract: A total of 202 revision hip arthroplasties in 178 patients, over a 2-year period, were evaluated prospectively. Intraoperative Gram stains were obtained from periprosthetic tissues in all cases. Of these, a definitive diagnosis of infection, using defined criteria, was established in 35 cases. Of these 35 patients, 17 had received antibiotics before surgery. The intraoperative cultures were positive in 8 of the 17 patients who had received antibiotics and 17 of the 18 patients who had not received preoperative antibiotics. In 1 infected case, intraoperative cultures of periprosthetic tissues failed to reveal bacterial growth, despite the fact that the patient received no preoperative antibiotics. Overall, there were 5 true-positive Gram stain results, 172 true-negative results, 3 false-positive results, and 22 false-negative results. The sensitivity of the Gram stain was 19%, specificity was 98%, predictive value of a positive test was 63%, and predictive value of a negative test was 89%. These results suggest that the intraoperative Gram stain is not a sensitive tool for the diagnosis of infection and should not be used when attempting to diagnose infection intraoperatively.
authors.affiliation: Department of Orthopaedics, University of British Columbia, Vancouver, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: Spangehl
authors.forename: E
authors.initials: E
authors.lastname: Masterson
authors.forename: B A
authors.initials: BA
authors.lastname: Masri
authors.forename: J X
authors.initials: JX
authors.lastname: O'Connell
authors.forename: C P
authors.initials: CP
authors.lastname: Duncan
mesh_terms: D019072:Antibiotic Prophylaxis; D019644:Arthroplasty, Replacement, Hip / Q000379:methods; D001424:Bacterial Infections / Q000175:diagnosis*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D007430:Intraoperative Care; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016459:Prosthesis-Related Infections / Q000175:diagnosis*; D012086:Reoperation; D012680:Sensitivity and Specificity; D013194:Staining and Labeling