Intermediate-Probability V/Q Scan

B. Intermediate (indeterminate) probability for PE

By PIOPED II criteria, INTERMEDIATE (indeterminate) probability includes: one moderate V/Q mismatch without corresponding chest X-ray abnormality; difficult-to-classify patterns not meeting high or low probability criteria; and studies with both high-probability and low-probability features. Intermediate probability scans are clinically challenging because approximately 30–40% of patients with intermediate scans have PE. Management depends on clinical pretest probability: low clinical probability + intermediate scan may allow withholding anticoagulation; high clinical probability + intermediate scan typically warrants further evaluation (CTPA) or empiric anticoagulation.