383. Rheumatic Disease Patients Have More Culture Negative Prosthetic Joint Infections: Are There Clinical Differences?

BACKGROUND: Rheumatic disease (RD) patients are at increased risk for prosthetic joint infections (PJI), however, diagnosis is challenging because active RD may mimic joint infection. We aimed to assess the incidence of culture-negative (CN) PJI in a population of RD and osteoarthritic (OA) PJI using an institutional PJI registry. Baseline clinical differences between CN-RD and culture-positive (CP)-RD as well as the relationship of culture negativity to survivorship of the prosthesis were also evaluated. METHODS: A retrospective cohort of hip and knee PJIs, from 2009 to 2016, were identified by ICD codes, and confirmed by chart review. RD cases were identified by ICD code and use of RD-specific medications. CN cases were defined as PJIs with no evidence of microbial growth in intraoperative cultures. Demographics, medications, microbiology, surgical therapy and outcome were abstracted. Baseline characteristics were evaluated using Fisher’s exact and Chi-Square tests. Kaplan–Meier estimates were used to calculate survivorship. RESULTS: 803 PJI cases were identified including 36 RD (33 rheumatoid arthritis and 3 systemic lupus erythematosus) and 771 OA. A higher proportion of RD PJI were CN (N = 10, 27%) vs. OA PJI (N = 109, 14%, P = 0.02). Fewer CN-RD cases met PJI histopathology criteria compared with CN-OA, (P = 0.08). On average, RD-CN were younger than OA-CN (59 vs 69, P = 0.01), but no different than RD-CP cases. One year survivorship of CN-OA and CN-RD were 87% and 66%, respectively and 47% for CP-RD. Comparing CN-RD vs. CP-RD, no difference was observed in age, smoking, diabetes, or Charlson comorbidities, but a trend toward higher prevalence of prior PJI in the CN-RD group. Clinically, no differences were found in surgical treatment (P = 0.92) or use of biologics and DMARDs (P = 0.12) between CN and CP RD patients. CONCLUSION: RD PJIs are more likely to be culture-negative than OA PJIs. Prior PJI, histopathology and better outcomes suggest biologic differences that should be explored further. [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.