1424. Association Between Erythrocyte Sedimentation Rate (ESR) Change and Treatment Failure in Patients with Osteomyelitis

BACKGROUND: Erythrocyte sedimentation rate (ESR) is monitored during therapy for osteomyelitis (OM) but the degree of reduction associated with treatment success remains unclear. METHODS: This retrospective cohort study evaluated patients treated for at least 2 weeks with intravenous (IV) antibiotics for OM through the VA St. Louis HCS from 1 January 2010 to 1 January 2018 with at least 2 ESR values during their therapy. Patients were excluded if they had comorbidities that could cause elevations in ESR. The primary outcome was the rate of treatment failure in patients achieving ≥50% decrease in ESR from baseline compared with those without a 50% decrease. Treatment failure was defined as a need for unplanned surgical intervention or re-initiation of antibiotic therapy for OM of the same anatomical site within 6-months after initial therapy was discontinued. The presence of diabetes, peripheral vascular disease (PVD), age >70, baseline creatinine clearance (CrCl) < 50 mL/minute, surgical intervention as part of initial therapy, and ESR reduction ≥50% from baseline were included in a univariate analysis with variables with a P < 0.2 included in a multivariate logistic regression model. RESULTS: A total of 143 patients were included; 74 patients with a ≥50% decrease in ESR and 69 patients with a decrease <50%. Mean initial ESRs were not different between groups (79.5±31 vs. 79.9 ± 32 mm/hour, P = 0.95), but end-of-treatment values were significantly higher in the <50% reduction group vs. ≥50% (20.6 ± 14 vs. 72.4 ± 42 mm/hour, P < 0.05, respectively). There were no baseline differences between groups in regards to age, rates of diabetes, PVD, CrCl < 50 mL/minute, initial surgical therapy management, or definitive vs. empiric therapy. Thirty percent (22/74) of patients with a ≥50% reduction in ESR failed treatment vs. 55% (38/69) in patients with a <50% reduction (P < 0.01). Only ESR reduction of ≥50% met criteria for inclusion in the multivariate regression model and was associated with a 65.5% relative risk reduction in treatment failure (OR 0.345; 95% CI 0.173–0.687; P = 0.002). CONCLUSION: Achieving an ESR reduction of ≥50% from baseline during treatment for OM was independently associated with a significant reduction in risk of treatment failure. DISCLOSURES: All authors: No reported disclosures.