Inappropriate use of D-dimer and impact on the test characteristics for deep vein thrombosis exclusion

Area of Science:

• Medical Diagnostics
• Clinical Pathology
• Thrombosis Research

Background:

• D-dimer testing is crucial for excluding deep vein thrombosis (DVT).
• Inappropriate D-dimer test requests can lead to diagnostic errors and increased healthcare costs.
• Evaluating the diagnostic utility of D-dimer in both appropriate and inappropriate clinical scenarios is essential.

Purpose of the Study:

• To determine the prevalence of inappropriate D-dimer testing for DVT exclusion.
• To compare the diagnostic value of D-dimer testing under appropriate versus inappropriate conditions.
• To assess the impact of inappropriate testing on negative predictive values (NPVs).

Main Methods:

• Retrospective chart review of D-dimer requests for DVT diagnosis at Siriraj Hospital, Thailand (January-September 2017).
• Analysis of D-dimer requests, Wells score, imaging, and coexisting conditions influencing D-dimer levels.
• Categorization of test requests into appropriate and inappropriate based on clinical guidelines and patient factors.

Main Results:

• Out of 300 DVT-related D-dimer requests, 53.6% were inappropriate due to testing in DVT-likely patients and 49.3% were relatively inappropriate due to coexisting conditions.
• Negative predictive values (NPVs) for DVT exclusion were significantly higher in DVT-unlikely patients (100% vs. 80%) and those without coexisting conditions (100% vs. 66.7%).
• High rates of inappropriate testing were observed, potentially leading to missed DVT diagnoses and unnecessary imaging.

Conclusions:

• A high rate of inappropriate D-dimer testing for DVT exclusion exists.
• Appropriate patient selection significantly enhances the negative predictive value of D-dimer assays.
• Implementing stricter patient selection criteria can improve diagnostic accuracy, reduce imaging overuse, and lower costs.