What scoring system can I use to diagnose pulmonary embolism in pregnancy, especially in a patient with a history of Deep Vein Thrombosis (DVT)?

Diagnostic Scoring Systems for Pulmonary Embolism in Pregnancy

The modified Wells score with a cutoff of 6 points is the most appropriate scoring system for evaluating suspected pulmonary embolism in pregnancy, especially in patients with a history of DVT. 1

Clinical Approach to PE Diagnosis in Pregnancy

Initial Assessment

• Pregnancy significantly increases PE risk, with PE being a leading cause of maternal mortality in developed countries 2, 3
• Standard clinical prediction rules like Wells or Geneva scores have not been formally validated in pregnancy, but recent evidence supports using the modified Wells score 1
• History of DVT is a significant risk factor that should be incorporated into risk assessment 4

Modified Wells Score in Pregnancy

The modified Wells score has shown excellent performance in pregnancy:

• 100% sensitivity and 90% specificity with a cutoff of ≥6 points 1
• 100% negative predictive value - no patients with a score <6 had PE 1
• Superior to other diagnostic tools like D-dimer, chest X-ray, blood gases, and EKG 1

Key Components of Modified Wells Score

1. Clinical symptoms of DVT (3 points)
2. Alternative diagnosis less likely than PE (3 points)
3. Heart rate >100 beats/min (1.5 points)
4. Immobilization or surgery in previous 4 weeks (1.5 points)
5. Previous DVT/PE (1.5 points) - particularly relevant for patients with DVT history
6. Hemoptysis (1 point)
7. Malignancy (1 point)

D-dimer Testing in Pregnancy

• Not recommended for excluding PE in pregnancy 2
• False negatives have been reported in pregnant women with documented PE 2
• Physiologic increases in D-dimer levels during pregnancy limit specificity 2

Diagnostic Algorithm for Pregnant Women with Suspected PE

1. Apply modified Wells score:

   • Score <6: PE unlikely but further testing still warranted given pregnancy status
   • Score ≥6: PE likely, proceed with imaging

2. Assess for DVT symptoms:

   • If DVT symptoms present, perform bilateral compression ultrasound (CUS) of lower extremities 2
   • Positive CUS: Begin anticoagulation without further imaging
   • Negative CUS: Proceed to chest imaging

3. Chest imaging pathway:

   • First obtain chest X-ray 2, 3
   • If CXR normal: Proceed with V/Q scan 2, 3
   • If CXR abnormal: Proceed with CTPA 2, 3
   • If V/Q scan non-diagnostic: Proceed with CTPA 2, 3

4. For patients with history of DVT:

   • Apply higher vigilance - history of DVT increases PE risk
   • Lower threshold for imaging studies
   • Consider the DVT history as adding 1.5 points to the Wells score

Special Considerations for Patients with Prior DVT

• Prior DVT increases risk of PE during pregnancy (odds ratio 9.4) 4
• History of superficial vein thrombosis is also a significant risk factor (odds ratio 9.4) 4
• Smoking further increases risk (odds ratio 2.4) and should be assessed 4
• These patients should be considered higher risk regardless of other clinical features

Limitations and Caveats

• The European Society of Cardiology (ESC) notes that data on clinical prediction rules in pregnancy are lacking 2
• Some studies show limited utility of both Wells and Geneva scores in pregnancy 5
• A 2014 retrospective study showed promising results for Wells criteria in pregnancy with 100% sensitivity and negative predictive value 6
• The most recent evidence (2018) suggests neither Wells nor Geneva scores perform optimally in pregnancy 5
• The modified Wells score with a higher cutoff (≥6) shows the most promise 1

Conclusion

For pregnant women with suspected PE, especially those with a history of DVT, the modified Wells score with a cutoff of 6 points offers the best available clinical prediction tool. However, given the potentially fatal consequences of missing PE in pregnancy, a low threshold for imaging is still warranted even with a reassuring score. The diagnostic pathway should include chest X-ray followed by appropriate imaging based on CXR results, with compression ultrasound considered when DVT symptoms are present.