The following are excerpts from Reference (1):
Venous thromboembolism (VTE) refers to disease states that include both deep venous thrombosis (DVT) and pulmonary embolism (PE).
Many clinical societies have made official guidelines for diagnosis of DVT  and for diagnosis of PE. In addition, the CLSI (Clinical and Laboratory Standard Institute) has a guideline for the exclusion of venous thromboembolism .
All the guidelines agree that VTE diagnosis can be based on pretest probability and D-dimer testing for patients with a sufficiently low probability of VTE:
- Negative D-dimer result – Rule out the patient
- Positive D-dimer result – Perform imaging for confirmatory diagnosis
Even though all international and local guidelines on VTE diagnosis agree that in patients with a sufficiently low pretest probability, D-dimer testing can be used to rule out VTE and that patients with a high pretest probability should either receive confirmatory imaging at once, and if that is not possible, they should be treated at once [1, 2, 3], it is not in these guidelines explicitly explained why D-dimer cannot be used to rule out VTE in high-pretest-probability patients.
This paper will explain and graphically illustrate why D-dimer cannot be used to rule out VTE in high-pretest-probability patients.
The pretest probability, also called the clinical probability score, is the probability that a person has a particular disease/condition before any test results are obtained. The pretest probability for large groups of people (such as the population of a country) is the same as the prevalence of the disease in that group.
The predictive values depend on the sensitivity and specificity of the test. However, the prevalence, i.e. the fraction of sick persons in the population tested, also has a strong impact on the predictive values.
For details please see the rest of the article.
(1) Why D-dimer tests cannot be used to exclude venous thromboembolism in patients with high pretest probability January 2015 by Susan Ekelund of acutecaretesting.org.
Note: acutecaretesting.com is a site of radiometeramerica.com. “Radiometer America is part of Radiometer Medical and a leading provider of advanced acute care solutions in the US.”