Tips from Other Journals

d-Dimer Test: A Normal Result Does Not Always Rule Out Pulmonary Embolism



FREE PREVIEW Log in or buy this issue to read the full article. AAFP members and paid subscribers get free access to all articles. Subscribe now.


FREE PREVIEW Subscribe or buy this issue. AAFP members and paid subscribers get free access to all articles.

Am Fam Physician. 2009 Oct 1;80(7):742.

Background: d-dimer testing is commonly used to help exclude venous thromboembolism (VTE), such as pulmonary embolism and deep venous thrombosis (DVT). Although several guidelines recommend that the d-dimer test be used in addition to the clinical probability of a thrombotic event, physicians may be tempted to use a normal d-dimer test result as stand-alone proof that VTE is unlikely. Gibson and colleagues prospectively evaluated consecutive patients with clinically suspected pulmonary embolism to determine how often d-dimer testing fails when clinical probability is not taken into account.

The Study: Initial risk was assessed using a clinical decision rule (see accompanying table). Patients with low clinical probability received d-dimer testing. Patients with low clinical probability and normal d-dimer levels of 0.5 mcg per L (0.5 mg per L) or less had pulmonary embolism ruled out. All other patients were further evaluated with spiral computed tomography (CT). Reimaging was performed in patients over the next three months if they had further symptoms indicating DVT or pulmonary embolism. Exclusion criteria included pregnancy, low-molecular-weight heparin use for longer than 24 hours at initial evaluation, and hypersensitivity to iodinated contrast fluid.

Table

Clinical Determination of Pulmonary Embolism Risk

Clinical finding Points

Clinical signs and symptoms of DVT (leg swelling and pain with palpation of the deep leg veins)

3

Alternative diagnosis is less likely than PE

3

Heart rate greater than 100 beats per minute

1.5

Surgery or immobilization in past four weeks

1.5

Previous DVT or PE

1.5

Hemoptysis

1

Malignancy (treatment in past six months or receiving palliation)

1


note: Patients with four points or fewer have low clinical probability of PE, and patients with more than four points have a high clinical probability of PE.

DVT = deep venous thrombosis; PE = pulmonary embolism.

Adapted with permission from Wells PS, 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):418.

Table   Clinical Determination of Pulmonary Embolism Risk

View Table

Table

Clinical Determination of Pulmonary Embolism Risk

Clinical finding Points

Clinical signs and symptoms of DVT (leg swelling and pain with palpation of the deep leg veins)

3

Alternative diagnosis is less likely than PE

3

Heart rate greater than 100 beats per minute

1.5

Surgery or immobilization in past four weeks

1.5

Previous DVT or PE

1.5

Hemoptysis

1

Malignancy (treatment in past six months or receiving palliation)

1


note: Patients with four points or fewer have low clinical probability of PE, and patients with more than four points have a high clinical probability of PE.

DVT = deep venous thrombosis; PE = pulmonary embolism.

Adapted with permission from Wells PS, 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):418.

Results: Overall, 1,722 persons were evaluated. The mean age was 54 years, and 78 percent were outpatients. Pulmonary embolism was ultimately identified in 378 patients (22 percent). Forty-five percent of patients with low clinical probability of VTE had a normal d-dimer test compared with 15.2 percent of patients with high clinical probability.

There were 563 patients with a normal d-dimer test; 477 of these patients were calculated to have low clinical probability and 86 to have high clinical probability. Five (1.1 percent) of the patients with a normal d-dimer test and low clinical probability were diagnosed with VTE during the follow-up period. In contrast, eight (9.3 percent) of the patients with a normal d-dimer test and high clinical probability were diagnosed with VTE, of whom all but one were diagnosed at baseline via spiral CT.

Conclusion: The authors recommend that physicians ignore a normal d-dimer test when there is a high clinical probability of VTE. This study reiterates the importance of clinical assessment when evaluating VTE, and that high-risk patients should have further testing, regardless of d-dimer levels.

KENNETH T. MOON, MD

Source

Gibson NS, et al. The importance of clinical probability assessment in interpreting a normal d-dimer in patients with suspected pulmonary embolism. Chest. October 2008;134(4):789–793.


Copyright © 2009 by the American Academy of Family Physicians.
This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP. Contact afpserv@aafp.org for copyright questions and/or permission requests.

Want to use this article elsewhere? Get Permissions


Article Tools

  • Print page
  • Share this page
  • AFP CME Quiz

Information From Industry

Navigate this Article