OC 70.1 - Outcome of Patients Treated with Antibiotics Prior to Pulmonary Embolism Diagnosis

Background: Differentiating between pulmonary embolism (PE) and respiratory tract infections may pose a diagnostic challenge due to overlapping symptoms, occasionally leading to the misdiagnosis of PE as an infection.

Aims: This study aimed to explore the characteristics and clinical implications of patients with PE initially treated for respiratory infections with antibiotics before receiving a PE diagnosis.

Methods: Patients diagnosed and treated for PE from January 2005 to May 2020 were identified from Østfold VTE Registry (TROLL). We compared clinical outcomes and patient-related factors including age, gender, cancer and other comorbidities in patients who had received antibiotics for respiratory tract symptoms within the four weeks preceding their PE diagnosis, with patients who had not.

Results: In total 2349 first-time PE patients were identified in TROLL. Of these, 275 had received antibiotics for respiratory tract symptoms the prior four weeks. The antibiotic-treated group had double the 30-day all-cause mortality rate compared to the untreated group; 12.36% and 6.22% respectively. The Hazard ratio estimated by cox regression was 2.05 with a p-value of 0.000. (Figure 1). No patient-related factors associated with higher mortality differed between the groups. The antibiotic-receiving group also featured other clinical factors indicative of a more severe course of illness from their PE, including higher mean PESI scores; 93.63 compared to 84.64 in the untreated group, as well as increased use of thrombolysis and hospitalization, longer hospital stay, more positive cardiac biomarker tests, and higher D-dimer values (Table 1).

Conclusion(s): Our findings indicate that patients treated with antibiotics tended to have a more severe PE with significantly worse mortality and other severity outcomes. Although we anticipate that treatment with antibiotics was indicative of misdiagnosis, we cannot exclude that PE was secondary to respiratory tract infections in some patients. Further research is needed to identify markers that can differentiate between the two conditions to avoid misdiagnosis.