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D-Dimers

Written by Mark Hill on .

D-Dimer and Wells Score

This section relates to current practice at Good Hope Hospital only. Heartlands and Solihull only offer laboratory D-Dimer testing for patients with suspected disseminated intravascular coagulation or sepsis. For patients with suspected deep vein thrombosis or pulmonary embolism, the service is provided as a point of care test within the Emergency Departments.

D-Dimer is a marker of endogenous fibrinolysis and is often used as a non-diagnostic marker in patients suspected of having deep-vein thrombosis or pulmonary embolism. It is also an important part of screening for disseminated intravascular coagulation.

For ?DVT/PE D-Dimer should only be used in conjunction with pre-test probability (PTP) scoring (Wells score). It is essential that this PTP information is clearly stated on the request form together with the clinical details. Without this information the laboratory cannot perform the analysis.

One correctly filled sodium citrate (blue top) is required for this test.

 

Calculating the Wells Score

Deep Vein Thrombosis

Clincal Characteristic

Score

Active cancer (patient receiving treatment for cancer within the previous 6 months or currently receiving palliative treatment)

1

Paralysis, paresis, or recent plaster immobilisation of the lower extremities

1

Recently bedridden for 3 days or more, or major surgery within the previous 12 weeks requiring general or regional anaesthesia

1

Localised tenderness along the distribution of the deep venous system

1

Entire leg swollen

1

Calf swelling by more than 3 cm compared with the asymptomatic leg (measured 10 cm below the tibial tuberosity)

1

Pitting oedema confined to the symptomatic leg

1

Collateral superficial veins (non-varicose)

1

Previously documented DVT

1

Alternative diagnosis at least as likely as DVT

-2

 Score: 0 = Low probability, 1-2 = Intermediate probability, >3 = High probability

Pulmonary Embolism

Clincal Characteristic

Score

Clinical symptoms of DVT

3

Alternative diagnosis is less likely than PE

3

Heart rate >100 bpm

1.5

Immobilisation or surgery within the previous 4 weeks

1.5

Previous objectively diagnosed DVT/PE

1.5

Haemoptysis

1.0

Malignancy with treatment within 6 months or palliative

1.0

 

 Score: 0 = Low probability, 1-2 = Intermediate probability, >3 = High probability

 

Interpreting the Wells Score

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A negative DDimer can safely rule out DVT/PE if the PTP is low in an outpatient. A DDimer test is not necessary if the PTP is Intermediate or High, further appropriate investigations should be performed. 

Other information to consider

  • DDimer is of no use for patients developing suspected DVT/PE during hospitalisation and therefore the test should not be requested for inpatients. This would apply to a patient who was admitted for reasons other than suspected DVT or PE and did not have symptoms or signs suggestive of DVT/PE on admission.
  • DDimer is of no use in patients already on warfarin or heparin of LMWH, false negative results can be seen.
  • In pregnant women, DDimer is of questionable value and it is not recommended for use in the diagnosis of DVT/PE.

 

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