New guidelines on the diagnosis and treatment of venous thromboembolism (VTE) were recently jointly issued by the American Academy of Family Physicians and the American College of Physicians. The guidelines are based on a systematic review of the evidence and are published, along with the systematic reviews, in the 2/2007 and 3/2007 issues of the Annals of Internal Medicine.
According to the reviews, there are 600,000 cases of VTE in the US annually, and the importance of early diagnosis and treatment is underscored by the morbidity and mortality associated with VTE. The authors state that 26% of patients with undiagnosed and therefore untreated PE will have a subsequent fatal embolic event, while another 26% will have a nonfatal recurrent event that can eventually be fatal. DVTs carry their own risk of complication: those proximal to the knee are associated with an increased risk of PE and those located only in the calf veins are associated with the postthrombotic syndrome .
The following summarizes the recommendations on diagnosis:
- Validated clinical prediction rules should be used to estimate pretest probability of VTE. The Wells prediction rules for PE and DVT were most frequently evaluated in the literature and have been validated. It is worth noting that these perform better in younger patients without comorbidiites or a history of VTE than they do in other patients.
- In patients with a low pretest probability of DVT or PE, obtaining a high-sensitivity D-dimer is a reasonable option. If negative, the test indicates a low likelihood of VTE in these patients. Data quoted in the article state that patients with a low pretest probability of DVT and a negative D-dimer had a 0.5% 3-month incidence of DVT, while the 3 month incidence in patients with intermediate and high pretest probabilities and a negative D-dimer was 3.5% and 21.4%, respectively.
- Ultrasound is recommended for patients with intermediate to high pretest probability of DVT in the lower extremities. More specifically, ultrasound has a high sensitivity and specificity for diagnosing proximal DVTs (those located proximal to the knee) in symptomatic patients. Important limitations to this recommendation are that ultrasound is less sensitive both in patients who have DVTs limited to the calf, as well as asymptomatic patients. Contrast venography remains the definitive test to evaluate for DVT.
- Patients with intermediate or high pretest probability of PE require diagnostic imaging studies. The gold standard remains pulmonary arteriography; helical CT’s sensitivity is, at the best, 90% with a specificity of 95%. Current multidetector CT technology may have higher sensitivity but further studies will be required to establish this hypothesis.
Next Week: Part 2 Recommendations on Treatment
Qaseem A et al. Current diagnosis of venous thromboembolism in primary care: A clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians. Ann Intern Med 2007 Mar 20; 146:454-8.
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