Ventilation Study Available (regular V/Q scan)

High probability of PE

–Two or more large mismatched ventilation/perfusion segmental defects. (or summed equivalent). (>75% of a segment = 1 large segmental equivalent, 25-75% of a segment(moderate defect) = 0.5 large segmental equibalent, <25% of a segment(small defect) does not count. )

Very low probability of PE

–Nonsegmental perfusion abnormalities only.(e.g. prominent hilum, cardiomegaly, linear atelectasis, costophrenic angle effusion, etc. ).

–Perfusion defect smaller than corresponding chest radiographic abnormality (regardless of ventilation findings).

–Stripe sign. (Peripheral perfusion in a defect.)

–Solitary triple-matched (V:Q:CXR) defects (<=1 segment) in an upper or middle lung zone. 

–Matched V/Q abnormalities in two or more zones of a single lung, with regionally normal chest radiograph.

–Solitary large pleural effusion. (Pleural effusion equal to one third or more of the pleural cavity with no other perfusion defect in either lung.)

–1 to 3 small (<25% of a segment) segmental defects.

Normal
–No perfusion defects

Nondiagnostic

–1 moderate to < 2 large segmental defects.

–1 matched (V:Q) defect, CXR negative.

–All other findings than those listed in the other categories.

Ventilation Study NOT Available (perfusion study only)

PE present

–Two or more large mismatched (Q: CXR) segmental defects.

PE absent

–Nonsegmental perfusion abnormalities only.(e.g. prominent hilum, cardiomegaly, linear atelectasis, costophrenic angle effusion, etc. ).

–Q defect< CXR lesion.

–1-3 small segmental defects.

–Solitary matched (Q:CXR) defect (<=1 segment)in mid or upper lung.

–Stripe sign. (Peripheral perfusion in a defect.)

–Solitary large pleural effusion. (Pleural effusion equal to one third or more of the pleural cavity with no other perfusion defect in either lung.)

Nondiagnostic

—All other findings than those listed in the other categories.