Identification of and solution for false D-dimer results.

Area of Science:

• Clinical chemistry
• Hematology
• Diagnostic assay development

Background:

• D-dimer (DD) levels are crucial for excluding deep venous thrombosis (DVT).
• Assay interference can lead to false D-dimer results, impacting clinical decisions.
• This study investigated using FDP/DD and Fib/DD ratios to detect and correct false DD results.

Purpose of the Study:

• To evaluate the reliability of fibrin degradation product (FDP)/D-dimer (DD) and fibrinogen (Fib)/DD ratios in identifying false DD results.
• To establish 95% confidence intervals (CIs) for these ratios to detect abnormal values.
• To verify identified false results using multiple dilution methods and alternative detection systems.

Main Methods:

• Analyzed 16,776 samples categorized into three groups based on D-dimer (DD) levels.
• Calculated the 95% confidence intervals (CIs) for the fibrin degradation product (FDP)/DD and fibrinogen (Fib)/DD ratios.
• Verified six identified abnormal DD results using multiple dilutions, cross-comparison with other instruments, and heterophilic blocking reagent (HBR) addition.

Main Results:

• The 95% CIs for FDP/DD ratios varied across DD level groups (A: 2.25-8.15, B: 2.86-10.58, C: 0.91-47.71).
• The 95% CIs for Fib/DD ratios also varied across DD level groups (A: 0.02-2.21, B: 0.68-8.15, C: 3.82-55.27).
• Six abnormal DD results were successfully identified and verified through multiple dilutions, inter-instrument comparison, and HBR testing.

Conclusions:

• The fibrin degradation product (FDP)/D-dimer (DD) ratio demonstrates higher reliability in detecting false DD results compared to the fibrinogen (Fib)/DD ratio.
• When the FDP/DD ratio falls outside its 95% confidence interval, verification using alternative methods is essential for accurate diagnosis.