D-Dimer
No matter whether you love or hate the D-dimer, it’s here to stay and is used daily - Brit Long MD & Alex Koyfman MD
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Diagnostics: Flex your D Dimer
Few diagnostic tests draw the ire that D dimer does. From ubiquitous to demonic, for most of this test’s existence it has been a dichotomous marker of clot, either a positive led to diagnostic testing and a negative was a clean pass. In this post, we will walk through why we should broaden our view of D dimer and adapt it to a variety of patients to properly risk stratify them.
BACKGROUND
D dimer is a natural fibrin degradation by product that occurs when a clot is being formed and lysed. D dimer was first discovered in 1973 in both human and bovine models, and appeared to be present when coagulation cascade was being activated. Initially used to detect…
Resources
Paucis Verbis: D-Dimer test
D-Dimer: To order or not to order? That’s the question when it comes to risk stratifying a patient for a pulmonary embolism with a low pretest probability. One should consider confounding conditions which may cause an elevated D-Dimer level. There’s always confusion about what may cause an elevated D-Dimer besides venous thromboemboli.
The D-Dimer Dilemma: It’s Use In Low-Risk PE
Over the past few decades, there have been many developments with regards to the application and use of D-Dimer in the investigations of patients presenting with possible Pulmonary Embolism.
With Age, Comes Wisdom and Maybe a new D-dimer Cutoff?
No matter whether you love or hate the D-dimer, it’s here to stay and is used daily. Granted, we order too many inappropriate D-dimer tests when evaluating patients with potential pulmonary embolism (PE) or deep venous thrombosis (DVT), but when used in the appropriately risk stratified patient, D-dimer can avoid further potentially harmful workups, radiation and contrast exposure.
Age-Adjusted D-dimer for Venous Thromboembolism (VTE)
Adjusts D-dimer cutoffs by age to help rule out VTE. Use in patients ≥50 years old presenting to emergency department as outpatients and are being worked up for PE with low to intermediate pretest probability. Do not use in high-risk patients (i.e., those who would proceed to imaging regardless of D-dimer result).
A Social Media Discussion About the Age-Adjusted D-Dimer Cutoff Levels to Rule Out Pulmonary Embolism Trial
Common themes that arose in the multimodal discussions included the heterogeneity of practices, D-dimer assays, provider knowledge about these assays, and prevalence rates in different areas of the world. This educational approach using social media technologies demonstrates a free, asynchronous means to engage a worldwide audience in scholarly discourse
Adjusting D-Dimer Test Thresholds Could Reduce Unnecessary Imaging
Nearly every strategy addressing the diagnosis of pulmonary embolism (PE) revolves around the D-dimer test. These crosslink fragments resulting from the cleaving of fibrin mesh by plasmin have doomed many an unsuspecting soul to computed tomography pulmonary angiograms (CTPAs). The oft-lamented primary challenge associated with dependence upon D-dimer is its lack of specificity.
Age Adjusted D-dimer in PE – The ADJUST-PE Study
The D-dimer assay has the potential to be a valuable test in the workup of PE as it is sensitive for thrombus formation. Unfortunately, specificity is low and indiscriminate use can lead to increased advanced imaging.
Age Adjusted D-Dimer Testing
The formula is: Age (years) x 10 ug/L for patients > 50 years of age. Example: Patient age 88 = age adjusted d-dimer of 880 ug/L
Age-Adjusted D-dimer: Is it Ready for Prime Time?
Age-adjusted D-dimer has been investigated in retrospective and some prospective studies. Although prospective trials are rare and no recent meta-analysis or clinical policy statement has been issued, there is an abundance of evidence that age-adjusted D-dimer increases specificity with minimal and acceptable decline in sensitivity in the low risk population.
Can an Age-Adjusted D-Dimer be Used to Safely Rule Out Pulmonary Embolism in Emergency Department Patients?
Yes, it appears that age-adjusted D-dimer (AADD) cut-off values, in combination with a non-high clinical probability, are safe and effective to essentially rule out pulmonary embolism in emergency department patients. Caution may be advised in patients older than 75 as they are slightly more likely to have a missed diagnosis of a clinically significant pulmonary embolism (PE).
Characteristics of emergency patients with markedly elevated D-dimer levels
Markedly elevated D-dimer levels can occur in emergency patients with various clinical situations, and is likely to indicate the presence of coagulopathy, rapid differential diagnosis was crucial for them.
D-Dimer and Pregnancy: The DiPEP Study
The study highlights the paucity of relevant literature, however, and reminds physicians of guidelines recommending against the use of D-dimer.
D-dimer for aortic dissection: the evidence
The easiest bottom line is that based on the current literature D-dimer should not be used in the evaluation of aortic dissection.
D-Dimer How To
Know your assay.
Dealing with D-dimer debacles
The D-dimer assay can be used as a “rule out” test in the emergency department when the pre-test probability of venous thromboembolism (VTE) is low.
Go Ahead, Age-Adjust the D-Dimer
If you include D-dimer as part of your practice to exclude pulmonary embolism, you’re probably already aware background levels gradually increase with age.
Should you adjust your D-dimer?
Wells and colleagues demonstrated that patients with a low pretest probability of having PE who have a negative D-dimer test can have PE safely excluded at the bedside. 3 Since then, there has been a concerted effort among thrombosis researchers to increase the proportion of patients who have PE excluded with D-dimer testing, based on the premise that computed tomography (CT) scanning should be avoided to reduce cost, time, and radiation exposure. This has led to age-adjusted D-dimer, 4 clinical probability-adjusted D-dimer, 5 and pregnancy-adjusted D-dimer.
The Age-Adjusted D-Dimer for PE Improves Care
Not a shift goes by in which EPs don't think about pulmonary embolism. Chest pain, shortness of breath, unexplained hypoxia, syncope, or tachycardia. You name it, PE enters the differential, and EPs routinely rely on well-studied, validated decision instruments to make the diagnosis.
The D-dimer Debate
So instead of using a fixed upper limit of 500 µg/L, I can use the formula of age x 10 to get the upper limit (for patients older than 50). So for an 80-year-old man, the upper limit for a VTE rule-out would be 80 x 10 = 800. Right? Right?!?! ..... Yeah, if only. Turns out, D-dimers are not the easiest things to measure.
The Diagnoses and Outcomes of Emergency Patients With an Elevated D-Dimer Over the Next 90 Days
Although not diagnostic for any condition, an elevated D-dimer level is a powerful predictor of mortality.
Wells + Dimer to Rule Out PE
Wells’ criteria and D-dimer can be used to safely exclude PE in patients with a low pre-test probability and negative D-dimer.
Diagnostics: Flex your D Dimer
Few diagnostic tests draw the ire that D dimer does. From ubiquitous to demonic, for most of this test’s existence it has been a dichotomous marker of clot, either a positive led to diagnostic testing and a negative was a clean pass.
Wells' Criteria
Objectifies risk of pulmonary embolism.
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