Objective of the study was to describe clinical and subclinical features and study sensitivity, specificity of MGIT in diagnosis of patients with smear negative pulmonary tuberculosis in Respiratory Department of Bach Mai hospital. The result showed that, on clinical: 78 percent cough (78 percent), chest pain (51.9 percent), fever (50 percent). Paraclinical: Chest X-rays: infiltration (72.9 percent)
Mantoux test positive (37.1 percent). PCR-BK positive (33.3 percent), Sp of PCR-BK (33.3 percent)
Sp of PCR-BK is 87.8 percent, positive predict value of PCR-BK is 75 percent and negative predict value of PCR-BK is 54.4 percent. MGIT positive in 38.9 percent of patients, Se (38.9 percent), Sp of MGIT (100 percent), positive predict value of MGIT (100 percent), negative predict value of MGIT (59.8 percent).