Diagnosing Pulmonary Embolism

Diagnosing PE — signs and symptoms

The signs and symptoms of pulmonary embolism (PE) include chest pain, shortness of breath, anxiety, and cough. These symptoms overlap with those for many other cardiac and pulmonary conditions.⁸ For this reason, the diagnostic process, and decisions regarding the need for imaging studies specifically designed to detect PE, should begin with a careful clinical examination and a determination of the likelihood that the patient has suffered PE.

Pulmonary embolus with haemorrhage

Diagnosing PE — tests and studies

PE is a common and potentially lethal condition that can cause death in all age groups. A good clinician should maintain a high index of suspicion for this condition, because prompt pulmonary embolism treatment can dramatically reduce the morbidity and mortality of the disease. Unfortunately, the diagnosis is often missed, because pulmonary embolism frequently causes only vague and nonspecific symptoms.^{283, 284}

Wells score for probability of PE

A clinical probability score can help estimate the likelihood of PE based on data from the history and physical examination, blood tests, and imaging study results.⁴² Scoring systems used in clinical practice include several key pulmonary embolism risk factors based on patient history. The Wells score is the most commonly used method to predict clinical probability of PE. This prediction rule has been revised several times since its development in 1995 to make it simpler and more accurate. ^{45, 282, 283, 284} The score includes the following elements:²⁸³

Points
Clinically suspected deep vein thrombosis (DVT)	3
Alternative diagnosis less likely than PE	3
Rapid heart rate	1.5
Immobilisation within past 4 weeks	1.5
History of DVT	1.5
Haemoptysis	1
Malignancy	1

A total score greater than 6 indicates a high probability of a PE, a score between 2 and 6 moderate probability and a score below 2 low probability.²⁸³

Imaging

The ventilation-perfusion scan has been the first-line study in patients with suspected PE for decades.⁴² A ventilation-perfusion scan indicating a high probability of PE provides sufficient evidence for the initiation of treatment, although it should be noted that a scan indicating a low probability of PE does not rule out the condition.⁴⁷ Helical computed tomography has a high sensitivity and specificity for detecting large pulmonary emboli but is generally unable to detect small ones. The current gold standard for diagnosis is pulmonary angiography. This is rarely a first-line diagnostic test, as it is more invasive than either ventilation-perfusion scans or helical CT.⁴⁸

Combined diagnostic methods

A combination of diagnostic methods can be used to assess patients with suspected PE. This approach, which includes the use of a simple clinical prediction rule, D-dimer testing and CT, was evaluated in a prospective cohort study involving over 3300 patients. This study showed this approach could be applied in 98.5% of eligible patients and that it effectively guided the clinical management decision in 97.9% of patients.²⁷⁶

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Article references

8 - Tapson VF. Acute pulmonary embolism. N Engl J Med. 2008;358(10):1037-1052.
283 - Wells P, Anderson DR, Rodger M, et al. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: increasing the models utility with the SimpliRED D-dimer. Thromb Haemost. 2000;83(3):416–420.
284 - Wells PS, Anderson DR, Rodger M, et al. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer. IAnn Intern Med. 2001;135(2):98–107.
42 - Ramzi DW, Leeper KV. DVT and pulmonary embolism: Part I. Diagnosis. Am Fam Physician. 2004;69(12):2829-2836.
45 - Wells PS, Anderson DR, Bormanis J, et al. Value of assessment of pretest probability of deep-vein thrombosis in clinical management. Lancet. 1997;350(9094):1795-1798.
282 - Wells PS, Ginsberg JS, Anderson DR, et al. Use of a clinical model for safe management of patients with suspected pulmonary embolism. Ann Intern Med. 1998;129(12):997–1005.
47 - The PIOPED Investigators. Value of the ventilation/perfusion scan in acute pulmonary embolism. Results of the prospective investigation of pulmonary embolism diagnosis (PIOPED). The PIOPED Investigators. JAMA. 1990;263(20):2753-2759.
48 - Blann AD, Lip GY. Venous thromboembolism. BMJ. 2006;332(7535):215-219.
276 - van Belle A, Büller HR, Huisman MV, et al; Christopher Study Investigators. Effectiveness of managing suspected pulmonary embolism using an algorithm combining clinical probability, D-dimer testing, and computed tomography. JAMA. 2006;295(2):172-179.

Angiography: Angiography is imaging of the blood vessels using X-rays or magnetic resonance tomography. The vessels are visualised by injecting contrast medium into a vein. Angiography is used to diagnose disorders of the blood vessels.
Computed tomography: Also know as CAT scan. A radiographic technique that uses a computer to assimilate multiple X-ray images into a two-dimensional cross-sectional image.