Using Quantitative D-Dimer to Determine the Need for Pulmonary CT Angiography in COVID-19 Patients

Area of Science:

• Medical Imaging
• Pulmonary Medicine
• Hematology

Background:

• COVID-19 is associated with hypercoagulopathy and increased risk of venous thromboembolism.
• Existing D-dimer screening models for pulmonary embolism (PE) may be less reliable in COVID-19 patients.
• A knowledge gap exists regarding optimal PE screening in COVID-19 positive individuals, leading to diagnostic challenges.

Purpose of the Study:

• To evaluate the effectiveness of quantitative D-dimer levels in identifying pulmonary embolism (PE) in COVID-19 patients.
• To determine if alternative D-dimer thresholds can aid in deciding the necessity of pulmonary CT angiography (CTA).

Main Methods:

• Retrospective analysis of 426 COVID-19 positive patients who underwent pulmonary CT angiography (CTA).
• Quantitative D-dimer levels were measured within 24 hours of CTA imaging.
• Comparison of D-dimer values between patients with and without PE.

Main Results:

• Of 426 patients, 18.5% had PE. The average D-dimer was significantly higher in the PE-positive group (9.15 μg./mL) compared to the PE-negative group (2.95 μg./mL).
• A D-dimer threshold of < 0.89 μg./mL maintained 100% sensitivity for PE exclusion while increasing specificity to 27.95%.
• A threshold of ≤ 1.28 μg./mL resulted in 97.47% sensitivity and 57.93% specificity for PE exclusion.

Conclusions:

• Alternative D-dimer thresholds are supported for excluding PE in COVID-19 patients.
• Higher D-dimer cut-off values may help reduce the rate of unnecessary pulmonary CT angiography scans in this population.