VARIABILITY IN THE DETECTION OF ENLARGED MEDIASTINAL LYMPH-NODES IN STAGING LUNG-CANCER - A COMPARISON OF CONTRAST-ENHANCED AND UNENHANCED CT

OBJECTIVE. Because CT protocols for staging lung cancer vary and littl e information exists regarding the diagnostic importance of using IV c ontrast material, our intent was to evaluate intra-and interobserver a greement in the detection of enlarged mediastinal lymph nodes, compari ng IV contrast-enhanced and unenhanced CT. SUBJECTS AND METHODS. Fifty patients with known or suspected bronchogenic carcinoma underwent une nhanced thoracic CT followed by contrast-enhanced CT. Three observers noted enlarged lymph nodes (>10 mm in the short axis) and assigned the enlarged nodes to American Thoracic Society nodal station designation s. Enlarged lymph nodes were grouped two ways: by assigning the exact number of enlarged lymph nodes found (zero, one, two, three, four or m ore), and by assigning whether at least one, or no, enlarged mediastin al lymph nodes were found at a station (''one or none''). Agreement le vels were determined for inter-and intraobserver interpretations using weighted kappa statistics and the McNemar test. RESULTS. The number o f enlarged lymph nodes with enhanced CT was 11%, higher than on unenha nced studies (418 versus 377; p = .044). Numbers of enlarged lymph nod es were different for five stations, however, the numbers were small e xcept for the right upper paratracheal station (2R) (contrast-enhanced , 68 enlarged lymph nodes; unenhanced, 44 enlarged lymph nodes; p = .0 14). With regard to all stations together, intraobserver agreement bet ween contrast-enhanced and unenhanced studies was almost perfect (kapp a range, .85-.94), and no difference was found for any observer in the proportion of patients with at least one enlarged lymph node. Interob server agreement was substantial or almost perfect for the total numbe r of enlarged lymph nodes. For specific stations, the lowest kappa val ue was .48 at 2R. One observer reported more patients with at least on e enlarged lymph node with contrast enhancement at station 2R (p = .03 1), Greater agreement existed between two observers at station 2R with contrast enhancement versus no enhancement (kappa = .85 versus .48; p = .02). Conclusions matched, and calculations of estimated kappa valu es gave similar results for determination of the specific number of en larged lymph nodes at a station and the ''one or none'' category. CONC LUSION. We found high agreement for intra-and interobserver interpreta tions for contrast-enhanced and unenhanced CT, although contrast-enhan ced CT revealed more enlarged lymph nodes, especially at station 2R.