Abstract: Objective  To analyze the diagnosis quality and related factors of initial smear-negative pulmonary tuberculosis(SN-PTB) registered in county dispensaries under National Tuberculosis Control Programme (NTP) in China. Methods   Four provinces were selected according to the registration level of national initial SN-PTB registered in 2006, one prefecture and two counties were selected in each province. The X-ray films and relevant clinical data of 60 cases of SN-PTB were sampled through cluster sampling method in each county. Their chests X-ray were photographed by digital camera, which were blindly re-read by national expert individuals and national group of experts. National experts included two experts in TB prevention and control, two in clinical TB and two in radiological TB respectively; National group of experts consisted of two TB prevention and control experts, two clinical and two radiological experts. The over-diagnosis was defined as re-read results by experts or group of experts who considered the chest X-ray did not meet the radiological changes of active TB. Univariate and multivariate logistic regression analysis were made to analyze the factors affecting the over-diagnosis, and explore the quality of  SN-PTB diagnosis. Results  The overall over-diagnosis rate is 20.78%（399/1920）, the average over-diagnosis rate of eight counties ranged from 10.83%（26/240）to 32.50%（78/240）, after the re-reading by experts, the over-diagnosis rate ranged from 10.21%（49/480）to 33.13%(159/480）. Logistic regression analysis showed over-diagnosis was affected by seven factors including chest X-ray quality, gender, age, doctor, PPD examination, BCG vaccination history and source of patient. Risk factors for over-diagnosis included 40≤age≤60（OR=2.007,95%CI=1.165-3.535）and over 60 years old（OR=1.710，95%CI=1.277-2.940）, female（OR=1.941，95%CI=1.226-3.102）, clinic doctor（OR=2.243，95%CI=1.793-4.27), PPD examination history（OR=1.985，95%CI=1.106-3.564）, BCG vaccination history（OR=2.773，95%CI=1.023-7.515）, quality of chest film“C”（OR=2.402，95%CI=1.006-6.995）and quality of chest film “D”（OR=10.694，95%CI=2.348-62.596）;protective factors included diagnosis of diagnostic group（OR=0.471,95%CI=0.440-0.643）,referral(OR=0.521,95%CI=0.313-0.865）and centralized recommendation(OR=0.437,95%CI=0.206-0.927）.Conclusion  The over-diagnosis rate of smear ne-gative pulmonary tuberculosis is high in China, the occurrence of over-diagnosis is affected by a variety of factors.

Key words: Tuberculosis,pulmonary/radiography, Radiography,thoracic, Quality cintrol