Interpretation

A normal D-dimer result of 500 ng/mL or less fibrinogen equivalent units (FEU) on the IL D-Dimer HS500 kit has a negative predictive value of approximately 100% (range 97%-100%) and is FDA approved for the exclusion of acute pulmonary embolism (PE) and deep vein thrombosis (DVT) when there is low or moderate pretest probability for PE or DVT.

D-dimer concentrations increase with age and, therefore, the specificity for DVT and PE exclusion decreases with age. For DVT or PE exclusion, in addition to clinical pretest probability, age-adjusted D-dimer cutoffs are suggested for patients older than 50 years of age.

Recent evidence suggests using clinical pretest probability and age-adjusted cutoffs to improve the performance of D-dimer testing in patients older than 50 years of age. In recent studies, when compared to a fixed D-dimer cutoff, age-adjusted D-dimer cutoff values (calculated as follows: age [years] x 10 ng/mL) resulted in equivalent outcomes and no additional false negative findings.(6-7)

Increased D-dimer values are abnormal but do not indicate a specific disease state. D-dimer values may be increased as a result of:

-Clinical or subclinical disseminated intravascular coagulation/intravascular coagulation and fibrinolysis

-Other conditions associated with increased activation of the procoagulant and fibrinolytic mechanisms such as recent surgery, active or recent bleeding, hematomas, trauma, or thromboembolism

-Association with pregnancy, liver disease, inflammation, malignancy, or hypercoagulable (procoagulant) states

The degree of D-dimer increase does not definitely correlate with the clinical severity of associated disease states.