What does a D-dimer level of 0.73 indicate?

D-dimer Level of 0.73: Interpretation and Clinical Significance

A D-dimer level of 0.73 μg/mL is mildly elevated above the standard threshold of 0.5 μg/mL, suggesting possible thrombotic activity, but this value alone is not diagnostic of any specific condition and requires clinical correlation.

Understanding D-dimer Values

D-dimer is a fibrin degradation product formed when cross-linked fibrin is broken down by plasmin during fibrinolysis. Its primary clinical utility lies in its high sensitivity and negative predictive value.

• Standard threshold: 0.5 μg/mL (500 ng/mL) 1
• Your result: 0.73 μg/mL (mildly elevated)
• Sensitivity: 98% for venous thromboembolism at the standard threshold 1
• Specificity: Generally low (34-56%) 1

Clinical Significance of Your Result

Possible Causes of Elevation

A D-dimer of 0.73 μg/mL represents a mild elevation that could be associated with:

• Venous thromboembolism (VTE): Including deep vein thrombosis (DVT) and pulmonary embolism (PE) 2
• Aortic pathology: Such as aortic dissection, though typically higher values are seen 2
• Cerebral venous thrombosis (CVT): Though levels vary with extent of thrombosis 2
• Physiological conditions:
  • Pregnancy (normal ranges increase progressively: 0.11-0.40 μg/mL in first trimester, 0.14-0.75 μg/mL in second trimester, 0.16-1.3 μg/mL in third trimester) 2
  • Advanced age (specificity decreases with age) 2
• Non-thrombotic conditions: Inflammation, recent surgery, cancer, infection 1, 3

Interpretation Framework

1. For VTE exclusion:

   • In low clinical probability patients, a D-dimer below 0.5 μg/mL can safely exclude VTE 2, 4
   • Your value of 0.73 μg/mL is above this threshold and cannot rule out VTE

2. For age adjustment:

   • If you are over 50 years old, an age-adjusted cutoff may apply: age × 10 μg/L 2
   • For example, if you are 70 years old, the cutoff would be 0.7 μg/mL

3. For pregnancy:

   • Your value of 0.73 μg/mL would be within normal range for second or third trimester pregnancy 2

Clinical Decision Making

When Further Investigation Is Warranted

• Non-pregnant, non-elderly patients: A value of 0.73 μg/mL warrants consideration of thrombotic disease based on clinical presentation 5

• If symptoms suggest VTE:

  • Leg pain/swelling → Consider compression ultrasound for DVT
  • Chest pain/dyspnea → Consider CTPA for PE 2

• If symptoms suggest aortic dissection:

  • Severe chest/back pain → Consider CTA of chest (sensitivity 99%, specificity 100%) 2

• If neurological symptoms present:

  • Headache, seizures, focal deficits → Consider MRI/MRV for CVT 2

When Observation May Be Appropriate

• Pregnant patients: A value of 0.73 μg/mL may be normal in second or third trimester 2
• Elderly patients: If age-adjusted cutoff exceeds 0.73 μg/mL, and clinical suspicion is low
• Recent surgery or known inflammatory condition: May explain mild elevation

Important Caveats

• D-dimer has high sensitivity but poor specificity for thrombotic disease 1
• False negatives can occur with:
  • Delayed testing after symptom onset
  • Thrombosed false lumen in aortic dissection
  • Short length of dissection
  • Young patient age 2
• Extremely high values (>5000 μg/L) are specific for serious illness (VTE, sepsis, cancer) 6
• Different D-dimer assays may produce different results; values are not transferable between methods 1

Bottom Line

A D-dimer of 0.73 μg/mL is mildly elevated and cannot exclude thrombotic disease in most non-pregnant, non-elderly patients. Clinical assessment and appropriate imaging should guide further management based on presenting symptoms and risk factors.