December 16, 2019

Background: The clinical diagnosis of pulmonary embolism (PE) can be challenging given its variable presentation, thus requiring dependence on objective testing. decision instruments such as PERC and the Wells’ score help stratify patients to low or high probability, enabling focused use of CT pulmonary angiography (CTPA) for diagnosis. However, despite these algorithms, there is evidence of increasing use of CTPA along with diminishing diagnostic rates (less than 10%). This combination results in the overdiagnosis of subsegmental PEs, unnecessary exposure to radiation and false positive results.

Though the D-dimer test has long been maligned for its low specificity the real issues around it rest in indiscriminate use and threshold value. In recent years, age-adjustment of the D-dimer and the YEARS algorithm have attempted to adjust the threshold in order to “rule-out” more patients without advanced imaging. The YEARS creates a two-tiered D-dimer threshold by first asking three questions:

  1. Are there clinical signs of DVT?
  2. Does the patient have hemoptysis? and
  3. Is PE the most likely diagnosis.

If the answer to all 3 questions is no, the D-dimer threshold is set at 1000 ng/mL FEU (500 ng/mL DDU) and if the answer is “yes” to any of the 3 questions, the D-dimer threshold is set at 500 ng/mL FEU (250 ng/mL DDU). More recently, the YEARS algorithm has been assessed in pregnancy.

Age-adjustment of the D-dimer assay simply multiplies 10 X the patients age (if using FEU and 5 X age if using DDU) and uses this number as the threshold for the test. This adjustment is applied to patients > 50 years of age. Age-adjustment of the D-dimer was endorsed by an ACEP clinical policy in 2018.

The PEGeD study is another attempt to show the safety of using an adjusted D-dimer threshold.

September 3, 2018

EM Journal Update: Safety of Using Wells’ Clinical Model With D-Dimer To Manage Patients In The ED With Suspected Pulmonary Embolism

Background: In the US, pulmonary embolism (PE) kills 100,000 people each year and over 360,000 new cases of PE are diagnosed each year (Horlander 2003). Currently, the gold standard for diagnosing PE is the computed tomographic pulmonary angiography (CTPA). Patients with PE present with varying symptoms, from anxiety and tachycardia, to shortness of breath and syncope. Thus, it is difficult to exclude this life-threatening diagnosis and thus far there is no validated method to exclude PE. Prior work from this group derived and validated Wells’ criteria for calculating clinical probability of PE, and using it to determine which patients should get serial ultrasonography, venography, or angiography after an equivocal ventilation perfusion (VQ) scan (Wells 1998). Now, this group examines how the D-dimer assay, together with Wells’ clinical model can help manage PE patients.

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