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The PIOPED Investigators. "Value of the ventilation/perfusion scan in acute pulmonary embolism. Results of the prospective investigation of pulmonary embolism diagnosis (PIOPED)". JAMA. 1990. 263(20):2753-2759.
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Clinical Question

In patients with clinical suspicion of acute pulmonary embolism, what is the diagnostic accuracy of V/Q scan for the diagnosis of acute pulmonary embolism?

Bottom Line

Low-probability and high-probability V/Q scans aided in ruling-out or diagnosing of PE when concordant with clinical assessment. An intermediate-probability V/Q scan is not of help in establishing diagnosis of PE.

Major Points

A high-probability scan usually indicates pulmonary embolism, but only a minority of patients with pulmonary embolism have a high-probability scan.



  • Prospective, multicenter
  • Setting: 6 clinical centers
  • Enrollment: January 1985 - September 1986
    • All patients considered for entry if V/Q scan or pulmonary angiogram requested
    • 5587 requested scans with 3016 (54%) eligible (2571 had requests cancelled, requests were made for diagnoses other than acute PE, or had contraindications to testing)
    • 1493 of 3016 (49.5%) consented for study, 1523 (50.5%) refused consent
    • 933 patients randomly selected for analysis
  • Follow-up:
  • Analysis:
  • Primary outcomes:


Inclusion Criteria

Patients greater than 18 years age, inpatient or outpatient, with symptoms that suggestive of PE (without standardized diagnosis algorithms) present within 24 hours of study entry

Exclusion Criteria

Patients with contraindications to angiography: Pregnancy, creatinine > 2.9mg/dL, or hypersensitivity to contrast material

Baseline Characteristics



Primary Outcome

Secondary Outcomes

Additional Analyses

Adverse Events



Sponsored by the National Heart, Lung, and Blood Institute (Bethesda, MD)

Further Reading