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Pulmonary Embolism: Difference between revisions
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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 ([[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.< | 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 [[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.< | 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 score|Geneva rule]]. More importantly, the use of ''any'' rule is associated with reduction in recurrent thromboembolism.< | There are additional prediction rules for PE, such as the [[Geneva score|Geneva rule]]. More importantly, the use of ''any'' rule is associated with reduction in recurrent thromboembolism. <cite>REFNAME9</cite> | ||
''The Wells score'':< | ''The Wells score'': <cite>REFNAME10</cite> | ||
*clinically suspected [[DVT]] - 3.0 points | *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 | ||
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*malignancy (treatment for within 6 months, palliative) - 1.0 points | *malignancy (treatment for within 6 months, palliative) - 1.0 points | ||
Traditional interpretation< | Traditional interpretation <cite>REFNAME3</cite><cite>REFNAME4</cite> <cite>REFNAME11</cite> | ||
* Score >6.0 - High (probability 59% based on pooled data< | * Score >6.0 - High (probability 59% based on pooled data <cite>REFNAME12</cite>) | ||
* Score 2.0 to 6.0 - Moderate (probability 29% based on pooled data< | * Score 2.0 to 6.0 - Moderate (probability 29% based on pooled data <cite>REFNAME12</cite>) | ||
* Score <2.0 - Low (probability 15% based on pooled data< | * Score <2.0 - Low (probability 15% based on pooled data <cite>REFNAME12</cite>) | ||
Alternative interpretation< | 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 [[D-dimer]] to rule out PE. | * 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 [[D-dimer]] level (shown in a [[blood test]]) is enough to exclude the possibility of thrombotic PE.< | 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 [[clinical utility of diagnostic tests|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 [[confidence interval|95% confidence intervals]] from 0.05 to 0.41%, though this review was limited by its use of only one [[randomized controlled trial|randomized-controlled clinical trial]], the remainder of studies being [[prospective cohort study|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 [[blood test]]s are done, in order to exclude important secondary causes of PE. This includes a [[full blood count]], [[coagulation|clotting status]] ([[prothrombin time|PT]], [[aPTT]], [[thrombin time|TT]]), and some screening tests ([[erythrocyte sedimentation rate]], [[renal function]], [[liver enzyme]]s, [[electrolyte]]s). If one of these is abnormal, further investigations might be warranted. | When a PE is being suspected, a number of [[blood test]]s are done, in order to exclude important secondary causes of PE. This includes a [[full blood count]], [[coagulation|clotting status]] ([[prothrombin time|PT]], [[aPTT]], [[thrombin time|TT]]), and some screening tests ([[erythrocyte sedimentation rate]], [[renal function]], [[liver enzyme]]s, [[electrolyte]]s). If one of these is abnormal, further investigations might be warranted. | ||