Introduction: Tuberculosis is an infectious disease caused by mycobacterium tuberculosis, which may affect the lung, but it can also affect other part of the body. 50% of the patient will be smear positive and easy to diagnose and in smear negative cases the diagnosis is difficult. So understanding the proportion of pulmonary tuberculosis in smear negative cases within modern Cat 1 ATT will help in early diagnosis and treatment which reduce or prevent mortality and morbidity due to pulmonary tuberculosis.

Primary objective: To find out the proportion of pulmonary tuberculosis in smear negative patients with suggestive radiological shadows in a tertiary care centre.

Secondary objective: What are the characteristics of radiological shadows which indicate that it could be tuberculosis

Study design: Prospective study

Study setting: Department of pulmonary Medicine, Govt. Medical College, Thiruvananthapuram

Methodology: A total of 398 patients with sputum AFB negative and x-ray chest shows radiological lesions were investigated and treated with antibiotic. Then further investigated and grouped into different diagnosis. The non diagnosed cases with radiological lesion were subjected for Cat 1 ATT and the response is observed and proportion of smear negative tuberculosis cases were assessed.

Conclusion: Patients above the age of 40 and male population were at risk of smear negative pulmonary tuberculosis. Comorbidities like diabetes COPD and risk factors like smoking were significant factors associated with pulmonary tuberculosis. Proportion of pulmonary tuberculosis in smear negative patients with suggestive radiological shadow in a tertiary care centre was 41%. characteristics of radiological shadows which indicate that it could be tuberculosis.

Keywords: Proportion, pulmonary tuberculosis, smear negative radiological lesions.

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Dr Ronald Win B

Additional Professor, Pulmonary Medicine, Govt Medical College, Trivandrum