Empiric Antibiotic Treatment and Diagnostic Imaging for Pneumonia

Resumé of thesis<br/><br/>Background<br/><br/>Antimicrobial resistance (AMR) is a threat to global health. A pivotal driver of AMR is the indiscriminate prescription of broad-spectrum antibiotics, which is largely attributable to diagnostic uncertainties about the specific pathogen and foci of the infection. Pneumonia is an infection frequently seen in the emergency department (ED), where timely and accurate diagnosis is crucial, not only to tailor the treatment but also to combat AMR. Danish guidelines for community-acquired pneumonia (CAP) recommend beta-lactamasesensitive penicillin and adding a macrolide or fluoroquinolone to provide coverage for Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae (LMC) pathogens in patients with high severity score. However, the efficacy of the current strategy in providing specific and comprehensive antibiotic treatment is still unknown. The chest X-ray (CXR) remains the primary imaging method for CAP. While standard-dose computed tomography (SD-CT) provides greater details and is considered the gold standard in imaging, its use is limited by the significant radiation involved. Emerging diagnostic imaging modalities include ultralow-dose CT (ULD-CT) and focused lung ultrasound (FLUS). ULD-CT is a modification of traditional SD-CT, limiting radiation exposure while maintaining adequate image clarity. FLUS, particularly when conducted by skilled operators using advanced ultrasound equipment, has been shown to have high sensitivity and specificity rates for the diagnosis of CAP. Nonetheless, the rise in handheld ultrasound (HHUS) devices and the relative scarcity of experienced FLUS operators warrants an examination of the accuracy of FLUS when performed by newly certified operators using HHUS. In light of these challenges, and given that often antibiotic treatment is commenced in the ED, this thesis seeks to evaluate current initial antibiotic prescription patterns arising from uncertain diagnoses and diagnostic imaging accuracy for CAP in the ED and imaging’s potential to reduce diagnostic uncertainty.