D-dimer in plasma (SimpliRED)

Introduction

Specific immunoassays for D-dimer can be performed directly on patient plasma. Plasma D-dimer levels reflect in vivo fibrinolysis.

Indications

• evaluation of suspected deep vein thrombosis
• assessment of risk for recurrence of DVT after cessation of anticoagulaton
• evaluation of suspected pulmonary embolism
• evaluation of suspected aortic dissection

Reference interval

• < 250-500 ug/L; < 0.5 mg/L, < 0.5 ug/mL
• threshold to rule out DVT/PE (specificity 47%)
  • < 500 ug/L; < 0.5 mg/L, < 0.5 ug/mL
  • < 750 ug/L if >= 60 years of age
  • age x 10 in ug/L*

* use of age-associated threshold reduces need for pulmonary CT angiogram

Clinical significance

• cross-linked D-dimer fragment of fibrin produced during fibrinolysis
• formation of D-dimer requires the action of both thrombin & plasmin
• plasmin degradation of fibrinogen alone does not result in D-dimer formation.
• increases in D-dimer occur with thromboembolism
  • Specificity 63% for DVT
  • Specificity of test for thrombosis is reduced in elderly to < 10% for patients > 80 years of age.
  • Sensitivity 81-88% for pulmonary embolism
    • 93% in segmental or larger arteries
    • 50% in subsegmental or smaller arteries
  • Specificity 52-61% for pulmonary embolism
• D-dimer adjusted for clinical probability in diagnosis of pulmonary embolism
  • < 1000 ng/mL for low-risk patients
• result in normal range does NOT rule out pulmonary embolism in patient with high pretest probablity
• Ref concludes D-dimer of limited clinical utlilty for diagnosis of pulmonary embolism.
• Sensitivity 100% for DVT in pregnant women
• a thrombosis without elevated D-dimer is rare (< 2-3%)
• for patients with a 1st DVT, a plasma D-dimer < 250 ng/mL measured 3 weeks after cessation of anticoagulation indicates low probability of recurrent DVT (3.7% vs 11.5 % 2 year risk, relative risk 0.3) vs plasma D-dimer > 750 ng/mL
• strategy of D-dimer testing & selective ultrasound as effective in the diagnosis of DVT as ultrasound for all R/O DVT (strategy dependent upon high pre-test probability of DVT for selecting patients for ultrasound)
• plasma D-dimer > 273 ng/mL (highest quartile) after MI* or unstable angina associated with increased 6 year risk of cardiovascular event & VTE* & 16 year risk of all-cause mortality, cardiovascular mortality & cancer mortality (observation seems independent of statin administration)

* MI=myocardial infarction, VTE=venous_thromboembolism

Increases

• primary & secondary fibrinolysis
• thrombolytic therapy with tissue plasminogen activator (tPA)
• thrombosis (use 500 ng/mL for cutoff)
  • deep vein thrombosis (DVT)
  • pulmonary embolism
  • arterial thromboembolism
  • disseminated intravascular coagulation (DIC)
  • localized intravascular coagulation
  • plasma D-dimer > 750 ng/mL after cessation of anticoagulation predicts recurrence of DVT
• vaso-occlusive crisis of sickle cell disease
• pregnancy, especially post-partum period
• malignancy
• surgery
• liver disease
• infection
• inflammation
• hematoma
• old age

Methods

• agglutination of D-dimer with monoclonal antibody fixed onto latex beads
• test read as macroscopic agglutination
• fibrinogen & fibrin split products do NOT react
• turn-around time 30 minutes

Specimen

• plasma (citrate)
• stable for 8 hours at room temperature
• stable for 6 months at -20 degrees C

More general terms

• fibrin degradation products in plasma

More specific terms

• fibrin D-dimer DDU in plasma
• fibrin D-dimer FEU in plasma

Additional terms

• D-dimer in plasma (SimpliRED)
• intravascular coagulation

Component of

• DIC panel

Patient information

D-dimer in plasma patient information