Table of Contents

1. Introduction
2. What is a D-Dimer Test?
3. Physiological Basis of D-Dimer Testing
4. Clinical Significance of D-Dimer Levels
5. Indications for D-Dimer Testing
6. Interpretation of D-Dimer Results
7. Company Solutions
8. References

Introduction

The D-Dimer test is a critical diagnostic tool used extensively in medical practice to assess blood clotting disorders. Understanding its implications and applications is vital in disease management and treatment planning.

What is a D-Dimer Test?

The D-Dimer test measures the presence of D-Dimer, a protein fragment produced during the breakdown of a blood clot. It is a fibrin degradation product and can be detected in serum following fibrinolysis, the process of clot degradation.

Physiological Basis of D-Dimer Testing

When a thrombus forms, the body initiates fibrinolysis to dissolve the clot. Plasminogen is activated to plasmin which breaks down the fibrin into D-Dimer fragments. A healthy individual typically has D-Dimer levels of less than 0.5 mg/L. Elevated levels indicate a potential thrombotic event.

Clinical Significance of D-Dimer Levels

Elevated D-Dimer levels are significant in diagnosing thrombotic conditions such as deep vein thrombosis (DVT), pulmonary embolism (PE), and disseminated intravascular coagulation (DIC). The specificity increases with negative results, effectively ruling out thrombotic conditions with <5% risk when D-Dimer levels are below the threshold.

Indications for D-Dimer Testing

Common indications include assessment of suspected thrombotic conditions, monitoring of coagulopathy in COVID-19 patients, and as part of diagnostic algorithms for venous thromboembolism (VTE). It's also used in conjunction with imaging studies to confirm diagnoses.

Interpretation of D-Dimer Results

Results are interpreted based on the specific assay used. Quantitative D-Dimer assays typically have a threshold of 0.5 mg/L or 500 ng/mL. Below the threshold indicates a low probability of thrombotic events, while levels above suggest further investigation. False positives can arise due to factors such as pregnancy, inflammation, and liver disease.

Company Solutions

Several companies provide solutions for D-Dimer testing, including:

• Siemens Healthineers: Offers the Atellica D-Dimer assay with a linear range of 0.05 to 35 mg/L.
• Roche Diagnostics: Provides the Elecsys D-Dimer test designed for quick assessment using immunoassay technology.
• Abbott Laboratories: Their Alinity i system offers precise D-Dimer quantification with automated processing.

References

1. Adam SS, Key NS, Greenberg CS. D-Dimer: A Diagnostic Marker for Thrombosis. Clinical Laboratory Science. 2009.
2. Aujesky D, Roy PM, Le Manach Y, et al. Validation of a clinical prediction rule to estimate the probability of pulmonary embolism. American Journal of Respiratory and Critical Care Medicine. 2006.
3. Kabrhel C. Clinician's guide to the diagnosis of deep venous thrombosis and pulmonary embolism. Circulation. 2011.