The ACEP Clinical Policies Committee regularly reviews guidelines published by other organizations and professional societies. Periodically, new guidelines are identified on topics with particular relevance to the clinical practice of emergency medicine, but for which no ACEP policy is available. This article highlights recommendations for the diagnosis of deep venous thrombosis (DVT), published in the 2012 clinical practice guideline of the American College of Chest Physicians.

Emergency physicians face a number of challenges when looking to make the diagnosis of deep venous thrombosis. First, DVT can present subtly, and clinical assessment alone is typically insufficient, requiring laboratory and imaging techniques to make the diagnosis.

Second, the development of a DVT within the patient’s venous system is a dynamic process, and diagnostic testing might miss the diagnosis in patients presenting early in the course of disease with a minimal clot burden. Third, the consequences of missing the diagnosis may be severe, as untreated DVT can lead to pulmonary embolism.

Clinicians now have several adjunctive technologies for assisting with the diagnosis, including D-dimer testing for the presence of fibrin split products, venous ultrasonography (proximal leg with compression, or whole-leg), and venography (typically by CT or MRI). However, this range of diagnostic testing options has resulted in wide practice variations.

In an attempt to standardize the evaluation of patients with suspected DVT, the American College of Chest Physicians published in February 2012 a clinical guideline on the diagnostic evaluation of these patients. While the document includes nearly 200 pages, the first few pages are user-friendly, highlighting specific recommendations to assist doctors in creating a diagnostic strategy. All recommendations are written in PICO format, and evidence is stratified using the GRADE working group process.

The most important concept from this guideline is that, rather than performing the same tests in all patients, the pretest probability of a DVT should determine the diagnostic pathway, much as is the current practice in the workup of pulmonary embolism. In patients with a low or moderate pretest probability of DVT, initial recommended tests include D-dimer or venous ultrasound.

There is a Grade 2C recommendation weakly favoring D-dimer testing over ultrasonography in this patient population, although patient characteristics (such as comorbid conditions causing elevated D-dimer levels) and technical factors (such as local availability and cost) should be taken into account. If either the D-dimer or venous ultrasound is negative, no further testing is warranted (Grade 1B). If the D-dimer is positive, venous ultrasound should be performed to confirm presence of a thrombus. This decision tree is presented as a graphical flow diagram in the guideline, and may represent the most widely applicable algorithm for the majority of patients presenting to the emergency department with suspicion for deep venous thrombosis.

In contrast, the initial test of choice for high-risk patients is venous ultrasound. The guideline states that D-dimer may be used to confirm a negative venous ultrasound but should not be used as the initial test. In all risk categories, including high-risk patients, the combination of a negative venous ultrasound and negative D-dimer negates the need for further testing.

The guideline recommendations become more complex if results of the diagnostic testing are contradictory. This predominantly arises in the setting of a positive D-dimer but a negative venous ultrasound. In this case, the venous ultrasound should be repeated in one week. This particular recommendation may be the most challenging to comply with for practitioners in emergency medicine, as follow-up appointments, particularly those involving diagnostic imaging, can be difficult to arrange.

Patients should be given clear discharge instructions recommending the repeat ultrasound, and explaining that while DVT is unlikely, the diagnosis has not been conclusively ruled out.

For any patient in whom pretest risk stratification is not performed, the best initial test is a venous ultrasound. If negative, a concurrent D-dimer test or a follow-up venous ultrasound in one week is indicated.

Some special circumstances bear mention. While DVT most typically occurs in the lower extremities, all of these recommendations remain in effect, without significant modification, whether the DVT is suspected in an upper or lower extremity. Also, pregnant patients require a separate diagnostic algorithm given the complications associated with D-dimer testing. In pregnant patients, if the venous ultrasound and D-dimer are both negative, no further testing or treatment is indicated.

However, most of these patients will have a positive D-dimer, and therefore any negative venous ultrasound in a pregnant patient with a positive D-dimer should be confirmed by repeat venous ultrasound in one week.

While on first reading these recommendations by the American College of Chest Physicians may seem complex, the underlying concept is simple: The greater the pretest probability of DVT, the more thorough the testing must be to exclude the diagnosis. The combination of negative venous ultrasound and negative D-dimer, or negative repeat venous ultrasound one week apart, is considered thorough enough to rule out DVT even in high-risk patients. Keeping this general principle in mind can help physicians in diagnosing and determining disposition of patients from the emergency department.

Reference

1. Bates SM, Jaeschke R, Stevens SM, et al. Diagnosis of DVT: antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest. 2012;141:e351S-e418S.

Dr. Bernstein is a senior resident in emergency medicine at Yale-New Haven Hospital, and is the 2011-2013 EMRA Representative to the ACEP Clinical Policies Committee.