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ntroduction:Iran with the rate of 17.9 cases in 100000 population had the seventeenth grade of tuberculosis incidence in 1998, indicating high prevalence rate of disease. Rapid diagnosis of disease is important for treatment of patients with tuberculosis and prevention of distribution in the community. This study was carried out to compare the radiologic manifestations of lung in smear negative and smear positive patients.
 
 
Materials and Methods: This descriptive study performed from 2004 to 2007 on patients referring to Imam Reza Hospital, Mashhad University of Medical Sciences. Sputum smear was examined for patients suspected to pulmonary tuberculosis. Positive smear for BK cases, were considered as smear positive patients. Bronchoscopy was performed for patients whose smears were negative for 3 times. Patients whose disease was confirmed with BAL or biopsy were supposed as smear negative patients. Finally, we collected information of 58 patients with smear positive tuberculosis and 64 patients with smear negative tuberculosis and compared radiologic manifestations of the two groups by chi-square and t test.
 
Results:In this study, there were 122 patients including 63 females (51.63%) and 59 males (48.36%). Patients' age range was 16 - 90 years old with the mean of 56.37 (SD = 18.8). The most common radiologic manifestation was Airspace consolidation, seen in 52 patients (42.6%) including 19 patients with smear positive and 33 patients with smear negative. Other radiologic features according to their prevalence consisted of: Airspace consolidationand Volume lossin 24 patients (19.7%) including 8 smear positive and 16 smear negative, Airspace consolidationandBronchogenic spreadin 17 patients (13.9%) including 16 smear positive and 1 smear negative, Airspace consolidation and Cavitationin 16 patients (13.1%) including 12 smear positive and 4 smear negative and Intrestitial opacities (Miliary)in 13 patients (10.5%) including 3 smear positive and 10 smear negative.
 
Conclusion: Generally, in 85 percent of patients with cavitary pulmonary tuberculosis, smear of sputum was positive, but just in less than 35 percent of patients with collapse and less than 25 percent of patients with intrestitial pattern, smear of sputum was positive.