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Published on: December 19, 2020
Using Quantitative D-Dimer to Determine the Need for Pulmonary CT Angiography in COVID-19 Patients
Gary Mikhjian1, Ahmad Elghoroury1, Keith Cronovich2
1Henry Ford Macomb.
Insights
COVID-19 patients with suspected pulmonary embolism (PE) may benefit from adjusted D-dimer thresholds. This study suggests higher D-dimer values can help rule out PE, potentially reducing unnecessary CT scans.
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.
Introduction:
COVID-19 has been frequently cited as a condition causing a pro-inflammatory state leading to hypercoagulopathy and increased risk for venous thromboembolism. This condition has thus prompted prior studies and screening models that utilize D-dimer for pulmonary embolism (PE) into question. The limited research to date has failed to provide tools or guidance regarding what COVID-19 positive patients should receive pulmonary CT angiography screening. This knowledge gap has led to missed diagnoses, CT overutilization, and increased morbidity and mortality.
Objective:
The purpose of this study was to examine the utility of the quantitative D-dimer lab marker in a convenience sample of 426 COVID-19 positive patients to assist providers in determining the utility of pulmonary CT angiography.
Methods:
The authors conducted a retrospective analysis on all COVID-19 positive patients within the Henry Ford Medical System between March 1st, 2020 through April 30th, 2020 who received pulmonary CT angiography and had a quantitative D-dimer lab drawn within 24 hours of CT imaging.
Results:
Our sampling criteria yielded a total of n = 426 patients, of whom 347 (81.5%) were negative for PE and 79 (18.5%) were positive for PE. The average D-dimer in the negative PE group was 2.95 μg./mL. (SD 4.26), significantly different than the 9.15 μg./mL. (SD 6.80) positive PE group (P < 0.05; 95% CI -7.8, -4.6). Theoretically, applying the traditional ≤ 0.5 μg./mL. D-dimer cut-off to our data would yield a sensitivity of 100% and specificity of 7.49% for exclusion of PE. Based on these results, the authors would be able to increase the D-dimer threshold to < 0.89 μg./mL. to maintain their sensitivity to 100% and raise the specificity to 27.95%. Observing a D-dimer cut-off value of ≤ 1.28 μg./mL. would reduce sensitivity to 97.47% but increase the specificity to 57.93%.
Conclusions:
These study results support the utilization of alternative D-dimer thresholds to exclude PE in COVID-19 patients. Based on these findings, providers may be able to observe increased D-dimer cut-off values to reduce unnecessary pulmonary CT angiography scans.
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