From the Guidelines
An elevated D-dimer test is significant for indicating an increased risk of thrombotic complications, such as deep vein thrombosis (DVT) and pulmonary embolism (PE), particularly in patients with COVID-19 or other critical illnesses.
Key Points
- A D-dimer level above the upper limit of normal is associated with critical illness, thrombosis, acute kidney injury, and death 1
- A D-dimer level > 5 mg/mL is associated with a high thrombotic risk, with a positive predictive value of at least 40-50% 1
- The use of D-dimer for diagnosing thrombosis is noteworthy, but it is a sensitive but nonspecific marker for VTE, and a negative result can aid in the exclusion of this diagnosis 1
- D-dimer testing has less usefulness in hospitalized and other acutely ill patients due to the high frequency of false-positive results 1
- The changes in D-dimer levels over time can help identify patients likely to develop thrombosis, with a D-dimer increment of 1.5-fold strongly associated with the diagnosis of thrombosis in COVID-19 patients 1
Clinical Implications
- In patients with a high thrombotic risk, defined by a D-dimer level > 5 mg/mL or a rapid increase of D-dimer level, therapeutic dose prophylactic anticoagulation and screening for thrombosis may be beneficial 1
- D-dimer testing can be used to exclude PE or DVT in patients with a low clinical probability, but its specificity decreases with age and in patients with cancer, hospitalized patients, and during pregnancy 1
- A negative D-dimer result in a highly sensitive assay safely excludes PE in patients with a low or moderate clinical probability, while a moderately sensitive assay excludes PE only in patients with a low clinical probability 1
Limitations
- D-dimer testing demonstrates not strictly comparable results due to high variability within and among methods, and the optimal cut-off value could be adjusted based on assay methodology 1
- Anticoagulant therapy lowers D-Dimers level, and the changes in D-dimer levels over time can be affected by various factors, including fibrinogen levels and fibrin degradation products 1
From the Research
Significance of Elevated D-dimer Test
- An elevated D-dimer test is a reliable and sensitive index of fibrin deposition and stabilization, indicating thrombus formation 2.
- However, D-dimer concentrations can be high in conditions unrelated to thrombosis, making its positive predictive value poor 2.
- Elevated D-dimer levels are associated with an increased risk of recurrent venous thromboembolism (VTE) and mortality 3.
- D-dimer testing can be used to diagnose and manage thrombosis-related clinical conditions, including:
- Diagnosis of venous thromboembolism (VTE) 2, 4
- Identification of individuals at increased risk of first thrombotic event (both arterial and venous) 2
- Identification of individuals at increased risk of recurrent VTE 2, 3
- Establishment of the optimal duration of secondary prophylaxis after a first episode of VTE 2
- Pregnancy monitoring 2
- Diagnosis/monitoring of disseminated intravascular coagulation (DIC) 2
Clinical Implications
- Extremely elevated D-dimer levels (> 5000 μg/l) are specific for serious illness, including VTE, sepsis, and cancer 5.
- An elevated D-dimer is an independent correlate of increased mortality and subsequent VTE across a broad variety of disease states 3.
- Tissue injury can cause elevated D-dimer levels, which may not normalize even after 14 days 6.
- D-dimer testing can be safely used in the management of acute VTE in emergency medicine, but attention should be paid to exclude conditions that may affect the accuracy of the test 4.