What are the next steps for a patient with elevated D-dimer levels?

Management of Elevated D-dimer Level of 1.38

For a patient with a D-dimer level of 1.38, the next step should be imaging with compression ultrasonography of the proximal veins to rule out deep vein thrombosis (DVT) or CT pulmonary angiography if pulmonary embolism (PE) is suspected, based on pretest probability assessment. 1, 2

Assessment of Pretest Probability

First, determine the pretest probability of venous thromboembolism (VTE) using a validated clinical decision rule:

1. For moderate pretest probability (which is likely with an elevated D-dimer of 1.38):

   • The positive D-dimer result (>0.5 μg/mL) requires further diagnostic imaging 1, 2
   • Proceed with proximal compression ultrasonography (CUS) or whole-leg ultrasound 1

2. For high pretest probability:

   • Proceed directly to imaging regardless of D-dimer result 1, 2
   • Either proximal CUS or whole-leg ultrasound is recommended over no testing 1

3. For low pretest probability:

   • Even with this elevated D-dimer, further testing would be indicated 2

Imaging Selection

Based on clinical presentation:

• For suspected DVT:

  • Proximal compression ultrasonography (CUS) is the recommended initial test 1
  • If proximal CUS is negative but D-dimer remains elevated, repeat proximal CUS in 1 week 1

• For suspected PE:

  • CT pulmonary angiography is the preferred imaging modality 2

• For suspected aortic dissection:

  • Consider CT angiography, as D-dimer has high sensitivity (96.6%) for aortic dissection 1

Special Considerations

• Age adjustment: For patients over 50 years, consider age-adjusted D-dimer cutoff (age × 10 μg/L) to improve specificity 2

• Critically elevated D-dimer: While 1.38 is elevated, it's not considered "critically elevated" (≥5 mg/mL), which would require immediate therapeutic anticoagulation 2, 3

• Other conditions causing D-dimer elevation:

  • Pregnancy, advanced age, cancer, inflammation, recent surgery, and COVID-19 can all cause D-dimer elevation without thrombosis 2, 4
  • These conditions may affect interpretation but don't change the need for imaging with this result

Follow-up Based on Imaging Results

• If imaging is positive for thrombosis:

  • Initiate appropriate anticoagulation therapy 1, 2
  • For DVT or PE, treatment rather than confirmatory venography is recommended 1

• If imaging is negative:

  • For proximal CUS: Consider repeat testing in one week if clinical suspicion remains high 1
  • For whole-leg US: No further testing is recommended if negative 1

Important Caveats

• D-dimer has high sensitivity but low specificity for VTE, making it more useful for ruling out than ruling in thrombosis 4, 5
• Never use D-dimer alone to diagnose thrombosis; imaging confirmation is required 1, 2
• An elevated D-dimer is independently associated with increased risk for incident VTE, recurrent VTE, and mortality, warranting thorough evaluation 6
• D-dimer assays lack standardization, with significant differences between testing methods 2

The elevated D-dimer of 1.38 requires further investigation with appropriate imaging based on clinical presentation and suspected thrombotic condition, as it exceeds the standard cutoff of 0.5 μg/mL.