Small nodules detected on chest radiography - Does size predict calcification?

Study objectives: To determine whether the likelihood of lung nodule calcif ication call be predicted from nodule size as measured on a chest radiograp h (CXR). Design: Retrospective review of CXRs of patients with lung nodules less tha n or equal to 1 cm in size detected oil CT scanning. CT images were used to identify calcifications and to provide spatial localization for readers to visualize nodules on a CXR and to measure their size. A subset of these no dules then was reexamined by different readers who did not view the CT scan s. Setting: Two university hospitals (Albuquerque, NM; Dallas, TX) and a US Ai r Force/Veterans Administration medical center (Albuquerque, NM). Patients: Two hundred thirty-six nodules in 185 patients Results: One half of the nodules (118) seen on CT scans could not be locate d on CXR, of which 8 (7%) were calcified. The prevalence of calcifications in the other 118 nodules visualized on CXRs was much higher (71 of 118 nodu les [60%]; p < 0.005). Among the nodules visualized on CXRs, those < 7 mm i n diameter (44 of 57 nodules [77%]) were more likely to be calcified than t hose greater than or equal to 7 mm in diameter (27 of 61 nodules [44%]; p < 0.005). Radiographs of 42 of the smallest nodules visualized on CXRs by th e initial readers later were examined prospectively by different readers wh o did not have access to the CT images. Thirty of 33 of the calcified nodul es (91%) but only 3 of 9 of the noncalcified nodules (33%) were detected (p < 0.005). These readers also recorded 40 additional small nodules that wer e not seen on CT scans, which were considered to be false-positives. Conclusions: Nodules detected on CXRs that measure < 7 mm in size are likel y to be calcified or to represent a false-positive finding.