D-dimer testing



Indications

D-dimer testing is of clinical use when there is a suspicion of deep venous thrombosis (DVT) or pulmonary embolism (PE) or disseminated intravascular coagulation (DIC). Most situations require a risk assessment score e.g. Wells score for DVT, Wells score for PE.

  • D-dimer are NOT indicated in patients with a moderate or high score (DVT or PE) as the result will not alter the need for further imaging(Doppler, CT pulmonary angiogram etc.)
  • D-dimers are NOT indicated in patients whose clinical presentation is unrelated to DVT, PE or DIC.
  • D-dimers ARE most useful for patients with a low probability of DVT or PE, where a negative result makes it unlikely that they have DVT or PE.

False positives:

Can be due to:

  • liver disease
  • high rheumatoid factor
  • inflammation
  • malignancy
  • trauma
  • pregnancy
  • recent surgery
  • advanced age

False negatives

  • False negative readings can occur if the sample is taken either too early after thrombus formation
  • If testing is delayed for several days.
  • Additionally, the presence of anti-coagulation can render the test negative because it prevents thrombus extension.


Content by Dr Íomhar O' Sullivan 31/01/2011. Last review Dr ÍOS 3/07/19