Christopher Study

Clinical Question

In patients with clinically suspected pulmonary embolism, does combined use of the Wells criteria in combination with a D-dimer test effectively select for patients with a true pulmonary embolism?

Bottom Line

Using the Wells criteria to categorize patients as "PE unlikely" or "PE likely," in combination with a D-dimer test, is an accurate and effective method for safely ruling out pulmonary embolism in patients where clinical suspicion exists, further reducing the need for additional imaging and exposure to radiation.

Major Points

The original Wells criteria, a scoring tool used to detect pulmonary embolism, placed patients in a "low," "moderate," or "high" risk category for PE. Regardless of classification, all patients would undergo D-dimer testing. If the D-dimer was abnormal, patients would undergo a VQ scan for definitive testing.

The Christopher Study used the same criteria from Wells score, but places patients into two categories instead of three: "PE unlikely" or "PE likely." This study showed that a negative D-dimer in patients categorized as "PE unlikely" may be safely discharged home as the incidience of 3-month PE was 0.5%. The algorithm also allowed safe exclusion of PE without unnecessary imaging in about one-third of the patients, reducing radiation exposure and facility resources.

Guidelines

Many guidelines including but not limited to the European Society of Cardiology, European Respiratory Society, American College of Chest Physicians, American Society of Hematology, and American College of Emergency Physicians recommend using D-dimer testing and clinical scoring tools similar to or adapted from the Wells score.

Design

• Multicenter, prospective, single-blind cohort study
• N=3,306
• Setting: 12 centers in the Netherlands
• Enrollment: November 2002 through December 2004
• Mean follow-up: 3 months post-assessment
• Analysis: intention-to-treat
• Primary outcome: incidence of symptomatic VTE during the 3 month follow-up, defined as:
  • Fatal pulmonary embolism
  • Nonfatal pulmonary embolism
  • Deep vein thrombosis

Population

Inclusion Criteria

• All consenting patients with clinically suspected pulmonary embolismn who presented during the study period

Exclusion Criteria

• More than 24 hours of LMWH
• Life expectancy < 3 months
• Pregnancy
• Geographic inaccessibility precluding follow-up
• Renal impairment
• Age < 18 years
• Allergy to IV contrast
• "Logistical reasons" (i.e. refusal of consent)

Baseline Characteristics

• Demographics: Age 53 years, female 57.4%
• Outpatients: 81.7%
• Duration of complaints (median): 2 days
• Paralysis: 2.8%
• Immobilization or recent surgery: 18.5%
• Previous VTE: 14.5%
• COPD: 10.3%
• Heart failure: 7.4%
• Malignancy: 14.4%
• Estrogen use, women: 23.1%
• Clinical symptoms of DVT: 5.7%
• Heart rate > 100: 26.2%
• Hemoptysis: 5.3%

Interventions

• In patients with clinically suspected PE, patients were stratified according their Wells score.
  • Patients with a Wells score ≤ 4 were classified as "Pulmonary Embolism Unlikely" and were then subjected to D-dimer testing:
    • Those with a normal D-dimer were considered negative for PE.
    • Those with an abnormal D-dimer > 500 ng/mL received CT imaging to further determine PE status.
  • Patients with a Wells score > 4 immediately went to CT imaging and did not receive D-dimer testing.

Outcomes

As this study had no comparator group, results are descriptive in nature and represent numbers of patients

Primary Outcomes

Total VTEs in Pulmonary Embolism Unlikely group and normal D-dimer test result

5

Fatal Pulmonary Embolism in Pulmonary Embolism Unlikely group and normal D-dimer test result

0

Total VTEs in patients with pulmonary embolism excluded by CT

18

• Where CT indicated normal impression

9

• Where CT indicated alternative diagnosis

9

Fatal pulmonary embolism in patients with pulmonary embolism excluded by CT

7

• Where CT indicated normal impression

3

• Where CT indicated alternative diagnosis

4

Total VTEs where pulmonary embolism was diagnosed by CT

20

Fatal pulmonary embolism in patients with pulmonary embolism diagnosed by CT

11

Secondary Outcomes

None reported

Subgroup Analysis

None reported

Adverse Events

None reported

Criticisms

• No comparisons to other validated diagnostic strategies
• Diagnosis of PE was made using CTA, where some studies suggest suggest pulmonary angiography is more sensitive for PE diagnosis. Thus, there is the potential for more false negatives from the CTA.

Funding

Grants from the participating hospitals