Incidental pulmonary embolism in cancer patients: Interobserver agreement on the diagnosis and extent with a focus on distal clots

BACKGROUND: The incidence of incidental pulmonary embolism (IPE) in cancer patients is increasing. There is scant information on the interobserver agreement among radiologists about the diagnosis of distal incidental clots and the actual radiologic extension of IPE. METHODS: A total of 88 contrast-enhanced computed tomography (CT) scans of cancer patients with IPE were reassessed blindly by two expert thoracic radiologists. First, 62 scans were reassessed and the interobserver agreement on most proximal extent of IPE was calculated between the two expert radiologists as well as between the initial and expert reading, using the kappa statistic. The sample was enriched with 26 additional scans for a total of 30 segmental and 29 subsegmental IPE to determine the interobserver agreement on distal clots. RESULTS: The level of agreement regarding the most proximal extent of IPE between the expert radiologists was very good (kappa 0.84; 95% CI, 0.73-0.95) and poor between the original radiologist and expert radiologists (kappa 0.39; 95% CI, 0.22-0.56). In the patients with segmental or subsegmental IPE on initial reading, the expert radiologists agreed with the segmental location in 12 out of 30 patients (40%) and with the subsegmental location in 17 out of 29 patients (59%). The interobserver agreement between the expert radiologists was good (kappa 0.68; 95% CI, 0.46-0.90) and moderate (kappa 0.48; 95% CI, 0.25-0.71), respectively. CONCLUSIONS: While the interobserver agreement between radiologists on the most proximal location of IPE in cancer patients appears to be fairly good, it decreases significantly for more distally located incidental clots.