Abstract: Objective To explore the value of CT in diagnosis of secondary smear negative pulmonary tuberculosis compared with chest X-ray film. Methods 118 smear negative pulmonary tuberculosis suspects were detected by chest X-ray film and CT scan,which included 76 cases of pulmonary tuberculosis and 42 cases of non-pulmonary tuberculosis.X-ray findings and CT manifestations were double-blindedly analyzed according to Receiver Operating Characteristic(ROC) curve. Results Calculated in the diagnostic threshold,the sensitivity,specificity,accuracy,positive prediction value and negative prediction value of X-ray findings were respectively 81.6%,61.9%,74.6%,76.3% and 69.2%,and those of CT findings were 93.4%,88.1%,91.5%,92.2% and 89.8%.Areas under the ROC curve(Az=0.958±0.043) of CT findings were significantly higher those of chest X-ray findings(Az=0.758±0.102) and chest X-ray findings with PPD,TB-AB tests(Az=0.833±0.071,P<0.01). Conclusion Chest CT scan plays the important role in diagnosis and differentiate diagnosis of smear negative pulmonary tuberculosis suspects.

Key words: pulmonary tuberculosis/diagnosis, tomography,X-ray computed