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|Performed by||Parnassus Hematology|
|In House Availability||24 hours, 7 days per week|
|Collection Instructions||Blue top filled to full extent of vacuum
|Container type||3.2% sodium citrate, Blue top tube
|Amount to Collect||2.7 mL|
|Sample type||Citrated plasma|
|Preferred volume||1.0 mL plasma|
|Min. Volume||0.5 mL plasma|
|UCSF Rejection Criteria||Lipemic or turbid samples|
|Processing notes||Deliver specimen immediately to Hematology
|Normal range||<400 ng/mL|
|Synonyms||FDD; Fibrin D-Dimers|
|Stability||Room temperature 4 hours|
|Turn around times||1 hour|
|Additional information||Reference Interval
The fibrin D-dimer (FDD) levels in 113 normal blood donors were used to calculate a reference interval using a transformed parametric method. This analysis yielded an upper limit of normal of 664 ng/mL with approximately 12% of FDD values >400 ng/mL (1). In APeX, the upper limit of normal has been set at 400 ng/mL in order to alert clinicians to the cutoff value for exclusion of venous thromboembolism (VTE; see below).
Evaluation for VTE, including pulmonary embolism (PE)
In patients at a low-to-intermediate clinical probability for PE and for whom imaging studies are under consideration, an FDD <400 ng/mL may permit diagnostic imaging (e.g., helical contrast computed tomography or ventilation/perfusion scan) to be avoided. Clinical correlation is advised in these settings. The FDD should only be ordered when there is reasonably substantive clinical suspicion for VTE/PE, as an elevated FDD is a nonspecific finding and can be elevated in the setting of recent fibrinolytic therapy, recent trauma or surgery, large hematoma, malignancy, sepsis or severe infection, cirrhosis, pregnancy, atherosclerosis, hemoglobinopathy, and age >60 years.
Some settings in which the FDD may not be appropriate to exclude VTE/PE include (2):
2. High probability for VTE/PE by clinical criteria
3. Current anticoagulation therapy
4. Suspected upper extremity thrombosis or thrombosis distal to knee
5. Substantial time elapsed between onset of thrombosis and laboratory testing (FDD has a half-life of approximately 7 hours and may be cleared from circulation following thrombosis)
6. Deficiency of fibrinolytic enzymes
Evaluation for disseminated intravascular coagulation (DIC)
Obtain a current prothrombin time (PT), activated partial thromboplastin time (aPTT), platelet count, and fibrinogen prior to ordering FDD. In an appropriate clinical context, an FDD >8200 ng/mL is suggestive of DIC. Serial studies following the demonstration of a positive result are not generally useful.
An acceptable ordering interval for the FDD is (1) 48 hours after last FDD or (2) 24-48 hours after last FDD with the most recent result <6000 ng/mL. If neither of these criteria are met, the FDD will be automatically canceled. Please contact the Hematology Lab Medicine Resident at 353-1747 if the clinical situation warrants more frequent re-evaluation of the FDD.
· Cloudy specimens (e.g., lipemic specimens) may yield artifactually low values. In some cases, such specimens cannot yield interpretable results.
· The presence of rheumatoid factor at a level greater than 50 IU/mL may lead to an over-estimation of the FDD.
1. UCSF in-house studies, 2004 and 2009.
2. Clinical Laboratory Standard Institute (CLSI). Document H59-A: Quantitative D-Dimer for the Exclusion of Venous Thromboembolic Disease. Approved Guideline.
|Last Updated||1/15/2014 10:30:08 AM|
If you have additional questions regarding this test, please call: 415-353-1667