From the Guidelines
The false positive rate for D-dimer tests is approximately 45.3%, as the specificity of D-dimer is reported to be around 54.7%. This means that roughly half of all positive D-dimer results occur in patients who do not actually have the thrombotic condition being tested for. The high false positive rate occurs because D-dimer levels can be elevated in many non-thrombotic conditions including pregnancy, inflammation, infection, cancer, recent surgery, advanced age, and liver disease 1. Some key points to consider when interpreting D-dimer results include:
- The test's sensitivity and specificity can vary across different types of tests and clinical probability for conditions like deep vein thrombosis (DVT) 1
- D-dimer quantification is crucial for the diagnosis of conditions like disseminated intravascular coagulation (DIC), where variability in test results can pose significant issues 1
- The use of different units to report D-dimer results, such as fibrinogen equivalent units (FEU) or D-dimer units (DDU), can lead to inaccurate results interpretation if not properly understood by laboratory personnel or clinicians 1
- The development of age-adjusted D-dimer cutoffs has improved the clinical utility of the test in older populations, where the specificity of the test decreases with age 1. Overall, while D-dimer is a useful test for excluding thrombosis, its high false positive rate means that positive results must be interpreted with caution and confirmed with further diagnostic testing.
From the Research
D-Dimer False Positive Rates
- The provided studies do not directly report the percentage of people with false positive D-Dimer results.
- However, it is mentioned in the study 2 that D-Dimer assays offer high sensitivity and low specificity, which can lead to false-positive results.
- The study 3 reports that 7.6% of patients with a positive age-adjusted D-Dimer (AADD) result were diagnosed with venous thromboembolism (VTE), implying that approximately 92.4% of patients with a positive AADD result did not have VTE, which could be considered false positives.
- The low specificity of D-Dimer assays is also mentioned in the study 4, which highlights the need for clinicians to be aware of the variability in D-Dimer assay performance and the characteristics of their institution's test when making clinical decisions.
- The study 5 reports that the introduction of D-Dimer assays, combined with clinical probability assessment, can help reduce the number of diagnostic imaging tests and hospital admissions, but it does not provide a specific percentage of false positive D-Dimer results.
- The study 6 focuses on the predictive value of D-Dimer levels for cardiovascular events in patients with peripheral arterial disease, but it does not report on the false positive rate of D-Dimer tests.