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803 Characteristics of patients with COVID-19 undergoing CT pulmonary angiography in the emergency department: a retrospective observational study
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  1. Annabel Rogers,
  2. Jonathan Brend,
  3. Dominic Pitt,
  4. Amelia Parker
  1. Chelsea and Westminster Hospital

Abstract

Aims/Objectives/Background The shared features of pulmonary embolism (PE) and COVID-19 create a diagnostic challenge for Emergency Departments. Raised D-dimer and CRP are predictive of PE, critical illness and mortality from COVID-19, however guidelines state there is insufficient evidence to recommend that biomarkers be used to guide practice to diagnose PE. This retrospective observational study analyses characteristics and biomarkers of patients with COVID-19 undergoing CT pulmonary angiography (CTPA) in the Emergency Department. The aim is to establish whether there is a role for D-dimer, CRP and Wells’ score to risk stratify patients with COVID-19 to guide CTPA imaging and enable early diagnosis of PE.

Methods/Design CTPA scans requested by two London Emergency Departments in April 2020, December 2020-February 2021 were identified. Inclusion: COVID-19 positive by PCR or radiographic appearances. Patient records screened to identify: gender, age, days since symptom onset, D-dimer and CRP. Exclusion: >30 days symptoms, chronic PE, already receiving anticoagulation or insufficient data. Wells’ scores calculated for patients diagnosed with PE.

Results/Conclusions 468 patients were included, with 47 diagnosed with PE on CTPA (prevalence=10%). D-dimer (ng/ml) is significantly higher in patients with PE compared to no PE (median 6154; IQR 2455-12092 v med 1221; IQR 787-2350, p<0.05). Odds ratio for PE with D-dimer ≥1000 compared to D-dimer <1000 = 26.8 (95% confidence interval: 3.66–196.29). Diagnostic testing: sensitivity 97.87%, specificity 36.82%, PPV 14.74%, NPV 99.36%. Mean Wells’ score in patients with PE=4 (3–7.5), with 53% (n=25) having a Wells’ score of 4 or less (’PE unlikely’).

D-dimer has a strong NPV for PE at values less than 1000ng/ml in the COVID-19 population, and therefore may have a role in ruling out PE and reducing CTPA scans in the Emergency Department. The Wells’ criteria, if used according to NICE guidance, would not indicate CTPA and potentially lead to delayed diagnosis in this patient group.

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