INTEROBSERVER VARIATION IN THE COMPUTED TOMOGRAPHIC EVALUATION OF MEDIASTINAL LYMPH-NODE SIZE IN PATIENTS WITH POTENTIALLY RESECTABLE LUNG-CANCER

Objective: To measure the reliability of the assessment of mediastinal lymph node size in computed tomographic (CT) scans of the thorax. Des ign: Observer agreement study in which radiologists, blinded to one an others' interpretation, were randomized to read 30 scans each. Populat ion: Sixty scans from patients with apparently operable non-small cell carcinoma of the lung were read by radiologists responsible for clini cal interpretation (clinical radiologists) and four radiologists with a special interest in thoracic CT (study radiologists). Measurements: Radiologists measured the size of left and right superior mediastinal nodes, aortic nodes, and the subcarinal nodes and, on the basis of whe ther any nodes accessible to mediastinoscopy were greater than 1 cm, r ecommended whether mediastinoscopy be undertaken. Agreement was quanti fied using kappa, a measure of chance-corrected agreement. Results: Am ong all radiologists, agreement on whether there were any nodes larger than 1 cm for right superior mediastinal nodes was 0.68; for left sup erior mediastinal nodes it was 0.28; for aortic pulmonary nodes it was 0.62; for subcarinal nodes it was 0.58; and for any node greater than 1 cm and accessible to mediastinoscopy it was 0.61. The agreement was very similar when the analysis was restricted to the study radiologis ts. Conclusion: Although the good level of overall agreement suggests that CT provides useful information in the evaluation of mediastinal l ymph node size, the disagreement was sufficient that it likely contrib utes to suboptimal sensitivity and specificity of CT in detecting tumo r spread reported in previous studies.