title: The Alpha-defensin Test for Periprosthetic Joint Infections Is Not Affected by Prior Antibiotic Administration.
abstract: BACKGROUND
  Previous studies have demonstrated that the administration of antibiotics to patients before performing diagnostic testing for periprosthetic joint infection (PJI) can interfere with the accuracy of test results. Although a single-institution study has suggested that alpha-defensin maintains its concentration and sensitivity even after antibiotic treatment, this has not yet been demonstrated in a larger multiinstitutional study.
  
  
  OBJECTIVE
  (1) For the evaluation of PJI, is prior antibiotic administration associated with decreased alpha-defensin levels? (2) When prior antibiotics are given, is alpha-defensin a better screening test for PJI than the traditional tests (erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], fluid white blood cells, fluid polymorphonuclear cells [PMNs], and fluid culture)?
  
  
  METHODS
  This retrospective study included data from 106 hip and knee arthroplasties with Musculoskeletal Infection Society-defined PJI from four centers. Of the 106 patients in this study, 30 (28%) were treated with antibiotics for PJI before diagnostic workup (ABX group), and 76 (72%) were not treated before the diagnostic workup (NO-ABX group). There were no differences in age, sex, joint, culture-negative rate, or bacteriology between groups. The patients in the ABX group had antibiotics initiated by physicians who commenced care before assessment for PJI by the treating surgeon's service. We compared the alpha-defensin levels and sensitivity between the ABX and NO-ABX groups. Additionally, the sensitivity of the alpha-defensin test was compared to that of traditional tests for PJI among patients on antibiotics.
  
  
  RESULTS
  The administration of antibiotics before performing the alpha-defensin test for PJI was not associated with a decreased median alpha-defensin level (ABX group, median 4.2 [range, 1.79-12.8 S/CO] versus NO-ABX, median 4.9 [range, 0.5-16.8 S/CO], difference of medians: 0.68 S/CO [95% confidence interval {CI}, -0.98 to 1.26], p = 0.451). Furthermore, the alpha-defensin test had a higher sensitivity (100%; 95% CI, 88.4%-100.0%) in diagnosing PJI among patients on antibiotics when compared with the ESR (69.0% [95% CI, 49.17%-84.72%], p = 0.001), the CRP (79.3% [95% CI, 60.3%-92.0%], p = 0.009), the fluid PMN% (79.3% [95% CI, 60.3%-92.0%), p = 0.009), and fluid culture (70.0% [95% CI, 50.6%-85.3%], p = 0.001).
  
  
  CONCLUSIONS
  The alpha-defensin test maintains its concentration and sensitivity for PJI even in the setting of antibiotic administration. Furthermore, among patients with PJI on antibiotics, the alpha-defensin tests demonstrated a higher sensitivity in detecting PJI when compared with the ESR, CRP, fluid PMN%, and fluid culture. The high sensitivity of the alpha-defensin test, even in the setting of prior antibiotic treatment, provides excellent utility as a screening test for PJI.
  
  
  METHODS
  Level III, diagnostic study.
authors: The Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, PA, USA.
authors: Alisina
authors: A
authors: Shahi
authors: The Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, PA, USA.
authors: Javad
authors: J
authors: Parvizi
authors: The Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, PA, USA.
authors: Gregory S
authors: GS
authors: Kazarian
authors: Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, OH, USA.
authors: Carlos
authors: C
authors: Higuera
authors: Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, OH, USA.
authors: Salvatore
authors: S
authors: Frangiamore
authors: Department of Orthopaedic Surgery, Mayo Clinic Phoenix, Phoenix, AZ, USA.
authors: Joshua
authors: J
authors: Bingham
authors: Department of Orthopaedic Surgery, Mayo Clinic Phoenix, Phoenix, AZ, USA.
authors: Christopher
authors: C
authors: Beauchamp
authors: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors: Craig Della
authors: CD
authors: Valle
authors: The Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, PA, USA.|The Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA, 19096, USA.
authors: Carl
authors: C
authors: Deirmengian
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D019072:Antibiotic Prophylaxis; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000295:instrumentation; D015415:Biomarkers / Q000378:metabolism; D003428:Cross Infection / Q000175:diagnosis* / Q000378:metabolism / Q000382:microbiology / Q000517:prevention & control; D004334:Drug Administration Schedule; D005260:Female; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D016459:Prosthesis-Related Infections / Q000175:diagnosis* / Q000378:metabolism / Q000382:microbiology / Q000517:prevention & control; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013582:Synovial Fluid / Q000378:metabolism / Q000382:microbiology; D016896:Treatment Outcome; D014481:United States; D023084:alpha-Defensins / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D015415:Biomarkers; D023084:alpha-Defensins