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Samwel Mikaye: D-Dimer – A Marker of Blood Clot Breakdown
Jun 8, 2026, 03:03

Samwel Mikaye: D-Dimer – A Marker of Blood Clot Breakdown

Samwel Mikaye, Medical Doctor at MSK, shared a post on LinkedIn:

“D-Dimer

Definition

D-dimer is a fibrin degradation product formed when a blood clot is broken down by fibrinolysis.

It reflects recent or ongoing clot formation and breakdown.

What it indicates

  • Active thrombosis plus fibrinolysis
  • Not specific for one disease (very sensitive, low specificity)

When D-dimer is raised

1. Thrombotic conditions

  • Deep vein thrombosis (DVT)
  • Pulmonary embolism (PE)
  • Disseminated intravascular coagulation (DIC)

2. Other causes (non-specific)

  • Infection / sepsis
  • Trauma or surgery
  • Pregnancy
  • Malignancy
  • Liver disease
  • Inflammation

Clinical use (VERY IMPORTANT in OSCE)

Rule-out test (NOT rule-in)

  • Low D-dimer – helps exclude DVT/PE in low-risk patients
  • High D-dimer – needs further imaging (not diagnostic alone)

D-dimer in DVT/PE pathway

  • First assess clinical probability (Wells score)
  • If low risk plus negative D-dimer – DVT/PE excluded
  • If high risk or positive D-dimer – do imaging (Doppler / CTPA)

Limitations

  • Very non-specific
  • Can be elevated in many conditions
  • Levels increase with age (elderly often have false positives)

‘D-dimer – D for Detection of clot breakdown’

Good to rule OUT, not rule IN thrombosis

D-dimer is a fibrin breakdown marker used to exclude DVT/PE in low-risk patients, but it is non-specific.”

Samwel Mikaye

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