Different D-Dimer Values Compared for Venous Thromboembolism Risk

D-dimer assays are generally evaluated according to cutoff points calibrated for of venous thromboembolism (VTE) exclusion and used to estimate the individual risk of recurrence after a first idiopathic event VTE.

The increase in age-dependent D-dimer levels has long been seen as a problem for the use of these assays in the work-up for VTE exclusion, and the assays performs poorly in the elderly population when traditional cutoff levels are adopted. Different cutoff systems have therefore been proposed and prospectively investigated to rule out pulmonary embolism.

Scientist at the University Hospital of Bologna (Italy) and their colleagues screened a total of 1,010 patients, whose index VTE event was idiopathic or associated with weak risk factors, and were included in the management protocol. Persistently negative D-dimer results were recorded in 528 patients (52.8%) who permanently interrupted anticoagulation and were followed up for a maximum of two years. In contrast, the remaining 482 patients had positive D-dimer results, and at the moment of their first positive result, were recommended to continue or resume anticoagulant therapy and followed by their anticoagulation clinic.

D-dimer levels were measured using the following commercial quantitative assays: VIDAS D-dimer Exclusion (bioMerieux; Lyon, France), Innovance D-DIMER (Siemens; Deerfield, IL, USA), HemosIL D-dimer HS or HemosIL D-dimer (Instrumentation Laboratory; Milan, Italy), and (v) STA Liatest D-dimer (DiagnosticaStago; Asnieres-sur-Seine, France). As cutoff values for negative/positive results, the centers used those specific for the assay, distinguishing those with results expressed as fibrinogen equivalent units (FEU) or non-FEU (D-dimer units) and for age and gender.

The predetermined cutoff levels for each assay, specific for age (lower in subjects less than 70 years), and gender (because it is lower in males), were used. In young subjects, the D-dimer-ULtrasonography in Combination Italian Study (DULCIS) low cutoff levels resulted in half the recurrent events that would have occurred using the other criteria. In elderly patients the DULCIS results were similar to those calculated for the two age-adjusted criteria. The adoption of traditional VTE exclusion criteria would have led to positive results in the large majority of elderly subjects without a significant reduction in the rate of recurrent event.

The authors concluded that the low cutoff levels adopted in the DULCIS study for young subjects resulted in more young patients who resumed anticoagulation with subsequent increased protection from recurrent events in this population that is at high risk of recurrence. In elderly patients, the high DULCIS cutoff points led to results similar to those calculated for the two age-adjusted criteria; the adoption of VTE exclusion criteria would have led to positive results in the large majority of subjects, without a significant reduction in the rate of recurrent event. The study was published on September 12, 2015, in the journal International Journal of Laboratory Hematology.

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