PIOPED vs Modified PIOPED II criteria

Question 1

What is PIOPED?

Answer 1

-Trial that led to the development of criteria for the determining risk of PE on VQ and CXR
-Grouped findings based on size and number of match/mismatched perfusion defects

Question 2

High probability risk category for PIOPED

Answer 2

-Findings likely due to PE
-PE Dx in >80% of cases

Question 3

Intermediate probability risk for PIOPED

Answer 3

-Findings nonspecific
-Between high and low (20-80%)
-Reserved for technically inadequate studies

Question 4

Low probability risk for PIOPED

Answer 4

-Findings unlikely due to PE
-PE Dx in <20% of cases

Question 5

Normal

Answer 5

No perfusion defects

Question 6

What categories does PIOPED II classify for VQ

Answer 6

High probability: >85%
Low probability: <10%
Normal scans

Question 7

Describe modified PIOPED II high probability

Answer 7

• V/Q has 2 or more large segmental mismatches
  -Normal CXR

Question 8

Describe modified PIOPED II very low probability

Answer 8

-Non-segmental defects
-Perfusion defect smaller than CXR abnormality
-1-3 small segmental perfusion defects
-Stripe sign perfusion defect
-Triple matched V/Q CXR defects in upper or middle lung
-Matched V/Q abnormalities in 2 or more zones of a single lung
-Pleural effusion encompassing 1/3 or more of a single lung

Question 9

Describe modified PIOPED II normal results

Answer 9

-No perfusion defcts
-Exclude PE as a diagnosis

Question 10

Describe modified PIOPED II non-diagnostic results

Answer 10

All other findings

Question 11

What are the key differences in modified PIOPED II?

Answer 11

-Non-diagnostic category which demonstrates a move to read a V/Q scan as either being positive or negative
-Emphasizes that caution should be exercised in non-diagnostic category because many are still suspicious of PE (a single segment mismatched defect and clear CXR)
-Incorporation of clinical factors is an important inclusion rather than a simple non diagnostic finding

Question 12

Explain the PISAPED criteria

Answer 12

-Prospective investigative study of acute pulmonary embolism
-Used in Europe
-Difference: No ventilation scan, just V/Q and CXR
-Comparable to PIOPED II perfusion only criteria: Pe present, PE absent, non-diagnostic

Question 13

Explain the applications of SPECT V/Q

Answer 13

-Common practice in Canada and Europe
-SPECT has 92% sensitivity and specificity
-Positive or negative categories: at least 1 segmental or 2 sub-segmental defects must be present to confirm PE
-Available clinically

Question 14

What are non-segmental defects and their causes?

Answer 14

-Defects resulting from processes outside the pulmonary segments
-Pleural effusion: Variable appearance, seen more often in supine patients
-Effusions/Fibrosis: Defect running along fissures
-Adenopathy, pacemakers, masses evident on CXR

Question 15

Explain a mucus plug

Answer 15

-Non-embolic disease
-Mucus plug in one or more airways leads to hypoxia
-Potential to cause matched segmental defects on V/Q