Effect of diagnosis level of certainty on adherence to antibiotics' guidelines in ED patients with pneumonia: a post-hoc analysis of an interventional trial.

Background and Importance: Clinical diagnosis of community-acquired pneumonia (CAP) is difficult to establish with certainty. Adherence to antibiotic guidelines independently affects the prognosis of CAP patients.
Objective: We aimed to determine whether guidelines' adherence was related to CAP diagnosis level of certainty and could be reinforced accordingly to diagnosis improvement.
Design: Secondary analysis of a prospective, multicenter study, which evaluated the impact of early thoracic CT scan on diagnosis and therapeutic plan in patients with clinically suspected CAP visiting emergency departments.
Setting and Participants: In total 319 patients with clinically suspected CAP were enrolled in four emergency departments, Paris, France, between Nov 2011 and Jan 2013.
Outcome Measures and Analysis: We evaluated guidelines' adherence before and after CT scan and its relationship with CAP diagnosis level of certainty. Antibiotics were categorized as adherent according to 2010 French guidelines. CAP diagnosis level of certainty was prospectively classified by the emergency physicians based on a Likert scale as excluded, possible, probable or definite before and immediately after the CT scan. These classifications and therapeutic plans were also completed by an independent adjudication committee. Determinants of adherence were assessed using Poisson regression with robust variance.
Main Results: Adherence to guidelines increased from 34.2% before CT scan to 51.3% after CT scan [difference 17.1% (95% CI, 9.5-24.7)], meanwhile CAP diagnosis with high level of certainty (definite and excluded CAP) increased from 46.1 to 79.6% [difference 33.5% (95% CI, 26.5-40.5)]. Diagnosis level of certainty before CT scan was the strongest determinant of adherence in multivariate analysis (RR, 2.63; 95% CI, 1.89-3.67).
Conclusion: Antibiotic guidelines' adherence was poor and positively related to CAP diagnosis level of certainty. The results suggest that improvements in CAP diagnosis may increase adherence to antibiotic guidelines. Clinical trial registered with www.clinicaltrials.gov (NCT01574066).
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