EFFECT OF ANATOMIC DISTRIBUTION OF PULMONARY EMBOLI ON INTEROBSERVER AGREEMENT IN THE INTERPRETATION OF PULMONARY ANGIOGRAPHY

OBJECTIVE, This study examines the anatomic distribution of emboli on pulmonary angiography and attempts to determine the relationship of ve ssel size to interobserver agreement, two factors having important imp lications in comparing pulmonary angiography with cross-sectional imag ing for pulmonary embolism. MATERIALS AND METHODS. One hundred twenty- five consecutive pulmonary angiograms were reviewed retrospectively by three interventional radiologists. Initial interpretations were recor ded and compared to determine interobserver agreement on a per-patient and per-embolus basis. Discordant interpretations were reviewed by al l radiologists for a consensus interpretation. RESULTS. Unanimous per- patient agreement occurred in 91% (114/125) of initial interpretations . The largest artery containing acute pulmonary embolism was segmental or larger in 24 patients (83% of patients with acute positive finding s, 19% of all patients) and subsegmental in only five patients (17% an d 4%, respectively). On a per-patient basis, initial interobserver agr eement averaged 45% and unanimous consensus agreement was achieved for 79% of patients having isolated subsegmental pulmonary embolism. Cons ensus readings altered initial per-patient interpretations for 30% of patients having only subsegmental pulmonary embolism; per-embolus inte rpretations were altered for 37% of all subsegmental emboli. CONCLUSIO N. Subsegmental emboli occurring as isolated findings are relatively r are. Approximately one third of subsegmental emboli and one third of p atients having isolated subsegmental emboli may be initially misdiagno sed on pulmonary angiography. Objections to cross-sectional imaging fo r pulmonary embolism based on the inability to detect subsegmental pul monary embolism when compared with pulmonary angiography should be ree xamined with this data in mind.