Does COVID-19 Infection Increase the Risk of Pulmonary Embolism?

May 14, 2026 updated by: University of Aberdeen

Does COVID-19 Infection Increase the Risk of Pulmonary Embolism? A Retrospective Case-control Study

The World Health Organization (WHO) declared the 2019 novel coronavirus (COVID-19) a pandemic on March 11, 2020. As of 19 July 2020, there have been 14.3 million confirmed cases and over 600,000 confirmed deaths. Up to 14% of infected patients develop interstitial pneumonia, which may evolve to acute respiratory distress syndrome.

COVID-19 associated pulmonary arterial microthrombosis and coagulopathy has prompted physicians to implicate pulmonary embolism (PE) as a potential cause for acute respiratory deterioration.

Literature review reveals few studies of varying size, quality and design. Recent meta-analysis reports venous thromboembolism in approximately 20% of COVID-19 patients. There has yet to be a case-controlled study which proves and quantifies the associated between COVID-19 and PE.Confirming and quantifying this association has numerous clinical implications for the treatment of critically unwell patients with COVID-19 infection. For example, clinicians will be more inclined to investigate and treat sudden deteriorations with the knowledge that pulmonary embolism is the commonest cause for said deteriorations.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

A retrospective case-control study of all patients who had a CT pulmonary angiogram (CTPA) at NHS Grampian between 3rd March and 20th June 2020 will be conducted.

CTPA reports and test results of Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) for COVID-19 will be reviewed via electronic medical records.

Patients with no COVID-19 RT-PCR test done within 7 days of the CTPA or the same clinical episode will be excluded. Patients who had repeat CTPAs, who are already known to have a PE, and who had CTPAs which are considered to be radiologically inadequate will be excluded.

Patients will be categorised into cases (positive PE) and controls (negative PE).

CTPA images of cases will be reviewed to collect further data about severity, distribution and right heart strain.

Patients' exposure status will also be determined (positive or negative for COVID- 19 infection).

The primary outcome is the number of pulmonary embolism cases related to COVID19.

The secondary outcomes are the severity, distribution of pulmonary embolism as determined by calculated Qanadli score. Presence of right heart strain.

Further data for the multivariate analysis will be obtained from the patient's electronic medical record. Specifically, we will collect data on risk factors for COVID-19 infection and PE to correct for confounding.

Statistical data analysis by various hypothesis tests and multivariate logistic regression will be conducted to determine the odds ratio of developing a PE, given positive COVID-19 infection.

Patients with a positive PE will have their scans reviewed to quantitatively assess their clot burden and degree of right heart strain. The former will be done by calculating a Qanadil score. The latter will be done my measuring the right ventricle- left ventricle ratio. This will allow for a comparison between COVID-19 infected and non-infected patients with PE.

Study Type

Observational

Enrollment (Actual)

347

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

12 years and older (Child, Adult, Older Adult)

Accepts Healthy Volunteers

N/A

Sampling Method

Probability Sample

Study Population

Acute hospital inpatients

Description

Inclusion Criteria:

-Patients who had a CT pulmonary angiogram at NHS Grampian between 3rd March and 20th June 2020.

Exclusion Criteria:

  • Patients with no COVID-19 RT-PCR test done within 7 days of the CT pulmonary angiogram or the same clinical episode.
  • Duplicate CT pulmonary angiograms.
  • Patients who are already known to have a pulmonary embolism.
  • Patients who had radiologically inadequate CT pulmonary angiograms.
  • Patients younger than 16 years old.
  • Patients who have incomplete or unavailable notes.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: Case-Control
  • Time Perspectives: Retrospective

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Pulmonary Embolism Positive
As determined by CT Pulmonary Angiogram
Diagnostic test: Exposure: Positive COVID-19 infection
Exposure: Positive COVID-19 infection as determined by RT-PCR
Diagnostic test: Exposure: Negative COVID-19 infection
Exposure: Negative COVID-19 infection as determined by RT-PCR
Pulmonary Embolism Negative
As determined by CT Pulmonary Angiogram
Diagnostic test: Exposure: Positive COVID-19 infection
Exposure: Positive COVID-19 infection as determined by RT-PCR
Diagnostic test: Exposure: Negative COVID-19 infection
Exposure: Negative COVID-19 infection as determined by RT-PCR

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Number of pulmonary embolism cases related to COVID-19.
Time Frame: 109 days
109 days

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Severity, distribution of pulmonary embolism as determined by calculated Qanadli score.
Time Frame: 109 days
Qanadli Score: The arterial tree of each lung is regarded as having 10 segmental PAs (three to the upper lobes,two to the middle lobe or lingula, and five to the lower lobes). The presence of an embolus in a segmental PA is scored as 1 point, and emboli at the most proximal arterial level are scored a value equal to the number of segmental PAs arising distally. To provide additional information on the residual perfusion distal to the embolus, a weighting factor is used for each value (0 for no defect, 1 for partial occlusion, and 2 for complete occlusion). An isolated subsegmental embolus is considered a partially occluded segmental PA and is assigned a value of 1. The maximum CT obstruction index is 40.
109 days
Presence of right heart strain associated with pulmonary embolism.
Time Frame: 109 days
As determined on CT by the presence of straightening of the interventricular septum and/or contrast reflux into the inferior vena cava and/or pulmonary artery measurements
109 days

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Aberdeen

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 1, 2021

Primary Completion (Actual)

March 3, 2022

Study Completion (Actual)

March 3, 2022

Study Registration Dates

First Submitted

November 19, 2020

First Submitted That Met QC Criteria

January 5, 2021

First Posted (Actual)

January 6, 2021

Study Record Updates

Last Update Posted (Actual)

May 19, 2026

Last Update Submitted That Met QC Criteria

May 14, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 1-073-20

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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