New D-Dimer Assay
From about midday on 3rd
February 2005 a new D-Dimer assay will be introduced at SydPath. The new assay will be a
quantitative assay with increased sensitivity to D-Dimer and results and the reference
interval will be substantially different.
·
Units: D-Dimer will
be expressed as mg/L fibrinogen equivalent units (FEU) which are equivalent to twice the
previous D-Dimer units.
·
Reference Limits:
The Upper Limit of Normal will be 0.5 mg/L FEU.
·
Exclusion of venous thromboembolism: In conjunction with a clinical pretest
probability scoring system (PTP), when the D-dimer is below a cutoff of 0.5 mg/L, it is
possible to rule out the diagnosis of deep vein thrombosis (DVT) and pulmonary embolism
(PE) in outpatients suspected of DVT or PE. This approach is not recommended for
hospital inpatients.
·
Investigation of other pathological conditions: eg disseminated intravascular
coagulation. Please note that results
will be 3 – 15 times greater than previously. Some of this increase is due to
a change of units, the remainder is due to the increased sensitivity to D-Dimer of the
monoclonal antibodies employed in the assay.
·
Test availability: The test is available 24 hours, with results
ready within 60 min of arrival of the specimen in the Haemostasis Laboratory.
·
Collection tube:
Blue top (citrate) tube is the only acceptable collection tube. Only 1 tube is required
for Coags plus D-Dimer.
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