From the Guidelines
A D-dimer level above 500 ng/mL (or 0.5 μg/mL) is generally considered concerning and may indicate the presence of abnormal blood clotting. This threshold is the most widely used cutoff in clinical practice, though some laboratories may use slightly different reference ranges [ 1 ]. When evaluating a patient for possible venous thromboembolism (VTE), such as deep vein thrombosis or pulmonary embolism, an elevated D-dimer warrants further investigation with imaging studies like ultrasound or CT angiography.
Key Considerations
- It's essential to note that D-dimer levels naturally increase with age, so some clinicians use an age-adjusted cutoff (age × 10 ng/mL for patients over 50) to improve specificity [ 1 ].
- D-dimer can be elevated in many conditions besides VTE, including pregnancy, recent surgery, cancer, infection, and inflammation, which is why it's more useful as a rule-out test when negative rather than a rule-in test when positive.
- A negative D-dimer below the cutoff in low to moderate risk patients can effectively exclude VTE without the need for additional imaging [ 1 ].
Diagnostic Approach
- For patients with low pretest probability of PE, the PERC criteria should be applied, and if all criteria are met, D-dimer testing is not necessary [ 1 ].
- For patients with intermediate pretest probability of PE, D-dimer testing is warranted, and an elevated level should prompt imaging studies [ 1 ].
- For patients with high pretest probability of PE, imaging studies should be performed directly, without the need for D-dimer testing [ 1 ].
From the Research
D-Dimer Levels and Concerning Values
- A D-dimer level above 5000 μg/l is concerning, as it may indicate severe underlying disease, mainly including venous thromboembolism (VTE), sepsis, and/or cancer 2.
- In patients with suspected pulmonary embolism, a D-dimer level above 500 ng/ml may be concerning, as it may indicate the presence of a pulmonary embolism 3.
- A study found that patients with D-dimer levels above 5000 ng/ml had a high prevalence of VTE, cancer, and pneumonia, and mortality was high when the levels were above 15,000 ng/ml 4.
- Another study found that a D-dimer level above 500 ng/ml at follow-up may indicate incomplete recanalization of pulmonary thromboemboli despite 6 months of anticoagulation after the first episode of acute pulmonary embolism 5.
- The optimal D-dimer cut-off level for identifying patients with deep vein thrombosis (DVT) may be around 1251 ng/ml FEU, with a sensitivity of 80% and specificity of 66.67% 6.
Clinical Significance of Elevated D-Dimer Levels
- Elevated D-dimer levels may indicate the presence of severe underlying disease, and clinical suspicion of severe underlying disease should be maintained even if sharply elevated D-dimers are a seemingly solitary finding 2.
- Ultra-high D-dimer levels (>5000 ng/ml) may be associated with a high risk of mortality, and patients with these levels should be carefully evaluated for underlying conditions such as VTE, cancer, and pneumonia 4.
- D-dimer levels may be used as a prognostic indicator for patients with COVID-19 infection, and ultra-high levels may indicate a poor prognosis 4.