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Modified PIOPED criteria for diagnosis of PE

The modified PIOPED criteria for diagnosis of PE determine the probability of PE following a VQ scan :

Levels of probability

High probability
  • 2 or more large mismatched segmental defects or equivalent moderate/large defects with a normal x-ray
  • any perfusion defect substantially larger than radiographic abnormality
Intermediate probability
  • multiple perfusion defects with associated radiographic opacities
  • greater than 25% of a segment and less than 2 mismatched segmental perfusion defects with:
    • normal radiograph
    • one moderate segmental
    • one large or two moderate segmental
    • one large and one moderate segmental
    • three moderate segmental
  • triple match : solitary moderate-large matching segmental defect with matching radiograph
  • difficult to characterize as high probability or low probability
Low probability
  • nonsegmental defects-small effusion blunting costophrenic angle, cardiomegaly, elevated diaphragm, ectatic aorta
  • any perfusion defect with substantially larger radiographic abnormality
  • matched ventilation and perfusion defects with normal chest radiograph
  • small subsegmental perfusion defects
Normal scan
  • no perfusion defects

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