From the Guidelines
D-dimer testing is a valuable screening tool for ruling out deep vein thrombosis (DVT) and pulmonary embolism (PE) in patients with low to moderate clinical suspicion, as stated in the most recent study 1.
Key Points
- A negative D-dimer result (typically <500 ng/mL FEU) in these patients effectively excludes DVT or PE without the need for further imaging, with a negative predictive value exceeding 95% 1.
- D-dimer has limited specificity as it can be elevated in many conditions including pregnancy, infection, inflammation, cancer, and advanced age 1.
- For this reason, a positive D-dimer result requires follow-up imaging such as ultrasound for suspected DVT or CT pulmonary angiography for suspected PE to confirm diagnosis 1.
- Age-adjusted D-dimer cutoffs (age × 10 ng/mL for patients over 50) improve specificity without compromising safety, as recommended by the American College of Physicians 1.
- D-dimer should not be used in high-risk patients, as a negative result does not reliably exclude thrombosis in this population 1.
Clinical Utility
- For optimal clinical utility, D-dimer testing should be combined with validated clinical prediction rules like Wells score or Geneva score to guide diagnostic decision-making 1.
- The test works by detecting fibrin degradation products that increase when clots form and break down, reflecting activation of both coagulation and fibrinolysis systems 1.
Recommendations
- D-dimer testing is recommended as the initial diagnostic test in patients with low to moderate clinical suspicion of DVT or PE 1.
- Imaging studies such as CT pulmonary angiography (CTPA) should be reserved for patients with high pretest probability of PE or those with a positive D-dimer result 1.
From the Research
D-dimer for DVT or PE Diagnosis
- The use of D-dimer as a stand-alone test to rule out deep vein thrombosis (DVT) has been suggested, with a failure rate of 1.8% (95% CI 0.8%-3.5%) 2.
- D-dimer levels can be used to exclude DVT or pulmonary embolism (PE) in patients with low or moderate clinical suspicion, with a sensitivity and negative predictive value of 89-100% and 95-100%, respectively 3.
- The D-dimer assay is inexpensive, automated, and has a rapid turnaround time, making it a useful tool for ruling out VTE 4.
- A negative D-dimer result can safely exclude DVT in symptomatic outpatients, with a negative predictive value of 98% (95%CI: 93-100%) 5.
Diagnostic Accuracy of D-dimer
- The sensitivity and specificity of D-dimer for DVT were 92% (95%CI: 73-99%) and 60% (95%CI: 52-67%), respectively, with a negative predictive value of 98% (95%CI: 93-100%) 5.
- For pulmonary embolism, the sensitivity and negative predictive value of D-dimer were 94-100% and 98-100%, respectively 3.
- The sequential use of a sensitive, rapid ELISA D-dimer and clinical score assessment can safely reduce the need for compression ultrasonography (CUS) testing by 40 to 60% 6.
Clinical Application of D-dimer
- D-dimer testing can be used to eliminate patients without VTE, but with low or moderate clinical suspicion, and can save healthcare facilities significant money by eliminating imaging studies 4.
- A normal rapid ELISA VIDAS D-dimer test result (< 500 ng/mL) has a negative predictive value of 98.4 to 99.3%, irrespective of clinical score 6.
- The combination of clinical assessment, a rapid ELISA VIDAS D-dimer, followed by CUS can reduce the need for helical spiral CT by 40 to 50% 6.