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==Diagnosis== | ==Diagnosis== | ||
The diagnosis of PE is based primarily on validated clinical criteria combined with selective testing because the typical clinical presentation ( | The diagnosis of PE is based primarily on validated clinical criteria combined with selective testing because the typical clinical presentation (shortness of breath, chest pain) cannot be definitively differentiated from other causes of chest pain and shortness of breath. The decision to do medical imaging is usually based on clinical grounds, i.e. the medical history, symptoms and findings on physical examination, followed by an assessment of clinical probability.<cite>Goldhaber</cite> | ||
The most commonly used method to predict clinical probability, the Wells score, is a | The most commonly used method to predict clinical probability, the Wells score, is a clinical prediction rule, whose use is complicated by multiple versions being available. In 1995, Wells ''et al.'' initially developed a prediction rule (based on a literature search) to predict the likelihood of PE, based on clinical criteria.<cite>REFNAME1</cite> The prediction rule was revised in 1998 <cite>REFNAME2</cite> This prediction rule was further revised when simplified during a validation by Wells ''et al.'' in 2000. <cite>REFNAME3</cite> In the 2000 publication, Wells proposed two different scoring systems using cutoffs of 2 or 4 with the same prediction rule. <cite>REFNAME3</cite> In 2001, Wells published results using the more conservative cutoff of 2 to create three categories.<cite>REFNAME4</cite> An additional version, the "modified extended version", using the more recent cutoff of 2 but including findings from Wells's initial studies<cite>REFNAME5</cite> <cite>REFNAME6</cite> were proposed. <cite>REFNAME7</cite> Most recently, a further study reverted to Wells's earlier use of a cutoff of 4 points <cite>REFNAME3</cite> to create only two categories. <cite>REFNAME8</cite> | ||
There are additional prediction rules for PE, such as the Geneva rule. More importantly, the use of ''any'' rule is associated with reduction in recurrent thromboembolism. <cite>REFNAME9</cite> | There are additional prediction rules for PE, such as the Geneva rule. More importantly, the use of ''any'' rule is associated with reduction in recurrent thromboembolism. <cite>REFNAME9</cite> | ||
''The Wells score'': <cite>REFNAME10</cite> | ''The Wells score'': <cite>REFNAME10</cite> | ||
*clinically suspected | *clinically suspected DVT - 3.0 points | ||
*alternative diagnosis is less likely than PE - 3.0 points | *alternative diagnosis is less likely than PE - 3.0 points | ||
* | *tachycardia - 1.5 points | ||
*immobilization/surgery in previous four weeks - 1.5 points | *immobilization/surgery in previous four weeks - 1.5 points | ||
*history of | *history of DVT or PE - 1.5 points | ||
* | *hemoptysis - 1.0 points | ||
*malignancy (treatment for within 6 months, palliative) - 1.0 points | *malignancy (treatment for within 6 months, palliative) - 1.0 points | ||
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Alternative interpretation <cite>REFNAME3</cite><cite>REFNAME8</cite> | Alternative interpretation <cite>REFNAME3</cite><cite>REFNAME8</cite> | ||
* Score > 4 - PE likely. Consider diagnostic imaging. | * Score > 4 - PE likely. Consider diagnostic imaging. | ||
* Score 4 or less - PE unlikely. Consider | * Score 4 or less - PE unlikely. Consider D-dimer to rule out PE. | ||
===Blood tests=== | ===Blood tests=== | ||
Early primary research has shown that in low/moderate suspicion of PE, a normal | Early primary research has shown that in low/moderate suspicion of PE, a normal D-dimer level (shown in a blood test) is enough to exclude the possibility of thrombotic PE. <cite>REFNAME13</cite> This has been corroborated by a recent systematic review of studies of patients with low pre-test probability (PTP) of PE and negative D-dimer results that found the three month risk of thromboembolic events in patients excluded in this manner was 0.14%, with 95% confidence intervals from 0.05 to 0.41%, though this review was limited by its use of only one randomized-controlled clinical trial, the remainder of studies being prospective cohorts. <cite>REFNAME14</cite> D-dimer is highly sensitive but not very specific (specificity around 50%). In other words, a positive D-dimer is not synonymous with PE, but a negative D-dimer is, with a good degree of certainty, an indication of absence of a PE. <cite>REFNAME15</cite> | ||
When a PE is being suspected, a number of | When a PE is being suspected, a number of blood tests are done, in order to exclude important secondary causes of PE. This includes a full blood count, clotting status (PT, aPTT, TT), and some screening tests (erythrocyte sedimentation rate, renal function, liver enzymes, electrolytes). If one of these is abnormal, further investigations might be warranted. | ||
===Imaging=== | ===Imaging=== | ||
[[File:Pulmonary embolism selective angiogram.JPEG|thumb|Selective | [[File:Pulmonary embolism selective angiogram.JPEG|thumb|Selective pulmonary angiogram revealing significant thrombus (labelled A) causing a central obstruction in the left main pulmonary artery. ECG tracing shown at bottom.]] | ||
[[File:Pulmonary embolism CTPA.JPEG|thumb | [[File:Pulmonary embolism CTPA.JPEG|thumb|CT pulmonary angiography (CTPA) showing a saddle embolus and substantial thrombus burden in the lobar branches of both main pulmonary arteries.]] | ||
[[File:Pulmonary embolism scintigraphy PLoS.png|thumb| | [[File:Pulmonary embolism scintigraphy PLoS.png|thumb|Ventilation-perfusion scintigraphy in a woman taking hormonal contraceptives and [[valdecoxib]].<br/>(A) After inhalation of 20.1 mCi of Xenon-133 gas, scintigraphic images were obtained in the posterior projection, showing uniform ventilation to lungs.<br/> | ||
(B) After intravenous injection of 4.1 mCi of | (B) After intravenous injection of 4.1 mCi of Technetium-99m-labeled macroaggregated albumin, scintigraphic images were obtained, shown here in the posterior projection. This and other views showed decreased activity in multiple regions.]] | ||
The gold standard for diagnosing pulmonary embolism (PE) is '' | The gold standard for diagnosing pulmonary embolism (PE) is ''pulmonary angiography''. Pulmonary angiography is used less often due to wider acceptance of CT scans, which are non-invasive. CT pulmonary angiography is the recommended first line diagnostic imaging test in most people. | ||
;Non-invasive imaging | ;Non-invasive imaging |
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