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Too many patients undergo a blood test to detect pulmonary embolisms.

New research from the University of Southern Denmark has led to new recommendations when suspecting pulmonary embolisms.

Casper Falster is a medical doctor and a PhD student at the Odense Respiratory Research Unit (ODIN) under the Department of Clinical Research, SDU, and Odense University Hospital.

In a new study published in The Lancet Hematology, Casper Falster, along with several collaborators, has reviewed the past 20 years' of guidelines for diagnostic investigation of pulmonary embolisms.

The review has shown, among other things, that the blood test D-dimer, should only be prescribed and carried out after the patient has been examined and assessed by a doctor. D-dimer has been used as a standard in some departments.


When one experiences an embolism, for example, in the lungs, protein remnants from the clot can subsequently be observed in the blood. D-dimer is the blood test analysis that can reveal these protein remnants. It is a highly effective blood test, but it also yields many false-positive results.

Upon receiving a positive result, further investigation is initiated. Fewer patients will undergo unnecessary analyses and test, if D-dimer is only prescribed and carried out for individuals who exhibit other signs pointing to an embolism. Elevated D-dimer can be a sign of an embolism, but it can also be caused by advanced age, pregnancy, cancer, or recent surgery.

Reduces the number of unnecessary scans

Previously, D-dimer in some departments has been prescribed and carried out at the first suspicion of a pulmonary embolism, for example, solely based on shortness of breath.

- The blood test provides many false-positive results. Therefore, it makes sense with a more well considered use of D-dimer. As doctors, we must react to a positive D-dimer with further investigations, says Casper Falster.

The additional investigations may include, for example, a CT scan, which could potentially expose the patient to unnecessary radiation.

New recommendations in Denmark

Casper Falster's results are already helping patients. "Vælg Klogt," a collaboration between the organisations ‘Danish Patients’ and ‘Danish Medical Societies’, has issued new recommendations for the use of D-dimer.

The recommendation is: Make a clinical assessment of the likelihood of a pulmonary embolism before testing D-dimer.

- There are two winners here - the patients who are spared unnecessary worry, and we as doctors can focus our energy on the examinations and assessments that are most relevant for the patient, says Casper Falster.

About the study

The study is a review of 13 clinical guidelines regarding the investigation when suspecting a pulmonary embolism. Only general guidelines were included. Guidelines specifically aimed at primary care, patients with cancer, pregnancy, og COVID-19 were excluded. Only English-language guidelines published after the year 2000 are selected, and the latest edition of the guideline is taken as the basis.

The following key topics were included: Examination and assessment by a doctor for the risk of a pulmonary embolism, the use of D-dimer, and the final diagnostic test.

Meet the researcher

Casper Falster is a medical doctor and a PhD student at the Department of Clinical Research. His oral PhD Defence Session takes place on October 13, 2023.


Read the study

The research study "Comparison of international guideline recommendations for the diagnosis of pulmonary embolism" is published in The Lancet Hematology by Casper Falster, Thomas Agerbo Gaist, Mikkel Brabrand, Mads Nybo, and others.

The Lancet Hematology

'Vælg Klogt'

‘Vælg Klogt’ is a collaboration between ‘Danish Patients’ and ‘Danish Medical Societies’. In the collaboration, they examine existing recommendations and attempt to minimize unnecessary treatments for the benefit of patients.

Editing was completed: 12.10.2023