Covid19NCT04696913
Does COVID-19 Infection Increase the Risk of Pulmonary Embolism?
An observational study of Covid19 and Pulmonary Embolism, run by University of Aberdeen at 1 site in United Kingdom.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 16 years and older
- Conditions the study is for
- Covid19, Pulmonary Embolism
- What is being tested?
- Exposure: Positive COVID-19 infection and Exposure: Negative COVID-19 infection
- How many people
- 347 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 1 Jan 2021to 3 Mar 2022
- Phase
- Observational
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 16 years and older
- All sexes
- Child, Adult, Older adult
Study population: Acute hospital inpatients
Who may be able to join
- -Patients who had a CT pulmonary angiogram at NHS Grampian between 3rd March and 20th June 2020.
Who cannot join
- 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.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: 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.
Read the 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.
- Conditions
- Covid19, Pulmonary Embolism
- Being tested
- Exposure: Positive COVID-19 infection, Exposure: Negative COVID-19 infection
- Keywords
- Case-Control Studies, Retrospective Study
- Medical subject headings
- COVID-19, Pulmonary Embolism
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Exposure: Positive COVID-19 infectionDiagnostic test
Exposure: Positive COVID-19 infection as determined by RT-PCR
Exposure: Negative COVID-19 infectionDiagnostic test
Exposure: Negative COVID-19 infection as determined by RT-PCR
| Study group | Role | What they receive |
|---|---|---|
| Pulmonary Embolism Positive | As determined by CT Pulmonary Angiogram Receives: Diagnostic Test: Exposure: Positive COVID-19 infection; Diagnostic Test: Exposure: Negative COVID-19 infection | |
| Pulmonary Embolism Negative | As determined by CT Pulmonary Angiogram Receives: Diagnostic Test: Exposure: Positive COVID-19 infection; Diagnostic Test: Exposure: Negative COVID-19 infection |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of pulmonary embolism cases related to COVID-19.
Measured: 109 days
Secondary outcomes (2)
Severity, distribution of pulmonary embolism as determined by calculated Qanadli score.
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.
Measured: 109 days
Presence of right heart strain associated with pulmonary embolism.
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
Measured: 109 days
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted6 Jan 2021
- Study start1 Jan 2021
- Primary completion3 Mar 2022
- Study completion3 Mar 2022
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Covid19Studies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Case-control
- Time perspective
- Retrospective
- Enrolment
- 347 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Aberdeen
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04696913
- Sponsor's protocol ID
- 1-073-20
- Status last verified
- May 2026
- First submitted
- 19 Nov 2020
- Last updated
- 19 May 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 19 May 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Does COVID-19 Infection Increase the Risk of Pulmonary Embolism? A Retrospective Case-control Study
- ClinicalTrials.gov ID
- NCT04696913
- Acronym / sponsor ID
- 1-073-20
- Conditions
- Covid19, Pulmonary Embolism
- Keywords
- Case-Control Studies, Retrospective Study
- Study type
- Observational
- Recruitment status
- Completed
- Enrolment
- 347 participants (actual)
- Lead sponsor
- University of AberdeenUniversity, hospital or other
- Study start
- 1 Jan 2021 (actual)
- Primary completion
- 3 Mar 2022 (actual)
- Study completion
- 3 Mar 2022 (actual)
- First posted
- 6 Jan 2021 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
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 design
- Observational model
- Case-control
- Time perspective
- Retrospective
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Pulmonary Embolism Positive | – | Diagnostic Test: Exposure: Positive COVID-19 infection, Diagnostic Test: Exposure: Negative COVID-19 infectionAs determined by CT Pulmonary Angiogram |
| Pulmonary Embolism Negative | – | Diagnostic Test: Exposure: Positive COVID-19 infection, Diagnostic Test: Exposure: Negative COVID-19 infectionAs determined by CT Pulmonary Angiogram |
Who may qualify
- Ages
- 16 years and older
- Sex
- All
- Age groups
- Child, Adult, Older adult
- Study population
- Acute hospital inpatients
Key inclusion criteria (1 listed)
- -Patients who had a CT pulmonary angiogram at NHS Grampian between 3rd March and 20th June 2020.
Key exclusion criteria (6 listed)
- 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.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Exposure: Positive COVID-19 infectionExposure: Positive COVID-19 infection as determined by RT-PCR | Diagnostic test | Pulmonary Embolism Negative, Pulmonary Embolism Positive |
| Exposure: Negative COVID-19 infectionExposure: Negative COVID-19 infection as determined by RT-PCR | Diagnostic test | Pulmonary Embolism Negative, Pulmonary Embolism Positive |
Primary outcome
Number of pulmonary embolism cases related to COVID-19.
Time frame: 109 days
2 secondary outcomes
Severity, distribution of pulmonary embolism as determined by calculated Qanadli score.
Time frame: 109 days
Presence of right heart strain associated with pulmonary embolism.
Time frame: 109 days
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 19 May 2026.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Covid19 and Pulmonary Embolism, run by University of Aberdeen at 1 site in United Kingdom.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 6 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 19 May 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Number of pulmonary embolism cases related to COVID-19. (time frame: 109 days). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 19 May 2026.