Nucleic acid amplification test and bronchoscopy improve the diagnostic accuracy of smear-negative tuberculosis

To determine whether the nucleic acid amplification (NAA) test on specimens collected by bronchoscopy improves the diagnostic accuracy of pulmonary tuberculosis (PTB) in sputum-negative patients.

Bronchoscopy was performed among smear-negative PTB suspects to collect respiratory specimens to assess the efficacy and accuracy of the Amplified Mycobacterium Tuberculosis Direct (AMTD) test in the diagnosis of PTB.

In 105 PTB suspects, 80 were finally excluded, of whom two were false-AMTD-positive. PTB (n = 25) was diagnosed in 10 patients culture-positive for Mycobacterium Tuberculosis (7/105 bronchial wash/bronchoalveolar lavage [BW/BAL] specimens, 6/315 expectorated sputum specimens [2 positive in 2 patients; 1 positive in 2 patients], and one with both), and in 15 patients with improvement after anti-tuberculosis treatment. Among the 25 PTB patients, 20 were AMTD-positive, of whom four were culture-positive. Three AMTD-negative patients were culture-positive. The sensitivity and specificity of AMTD were respectively 80.0% and 97.5%. The diagnostic yield was higher in respiratory specimens obtained at bronchoscopy and measured by AMTD than in conventional sputum or BW/BAL culture.

NAA testing on specimens collected using bronchoscopy provides a highly efficient and reliable approach in the diagnosis of PTB in smear-negative PTB suspects.