The solitary pulmonary nodule on chest radiography: Can we really tell if the nodule is calcified!

OBJECTIVE, This study was designed to assess the ability of radiologists to accurately detect calcification within a solitary pulmonary nodule with ch est radiography, MATERIALS AND METHODS. Thirty-five solitary pulmonary nodules that were exa mined by both posteroanterior and lateral chest radiography and on thin-sec tion CT were retrospectively identified. Fourteen radiologists blinded to t he results of CT assessed the nodules for the presence or absence of calcif ication using chest radiographs alone. The radiologists then assigned one o f six values on the basis of their confidence in that assessment. The accur acy and confidence values for each nodule were analyzed on the basis of the presence or absence of calcification as seen on CT. Receiver operating cha racteristic (ROC) curves were generated. RESULTS. The positive predictive value of a "definitely calcified" assessme nt was 0.93. Combining all levels of radiologists' confidence, the sensitiv ity of the chest radiograph in the detection of calcium was 0.50 and the sp ecificity was 0.87. There was no difference in the confidence levels report ed between the calcified and noncalcified nodules, and there was no correla tion of nodule size with accuracy or confidence level. CONCLUSION. The ability of radiologists to detect calcium in a solitary pul monary nodule by chest radiography was low, as defined by the ROC data. Of the "definitely calcified" nodules, up to 7% may not be calcified and may b e potentially malignant. Without documentation of long-term stability, a lo w threshold for recommending CT may be appropriate.