Objective: The purpose of this study was to compare the inflammatory activity of pulmonary lesions between active tuberculosis and nontuberculous mycobacterial (NTM) infection in acid-fast bacilli smear-positive non-HIV-infected patients using gallium-67 (Ga) scintigraphy.
Patients and methods: Twenty-four patients with culture-proven active pulmonary tuberculosis (PTB) and an additional 17 patients meeting the criteria of pulmonary NTM infection were enrolled into the retrospective study. The Ga uptake of the pulmonary lesion was assessed by visual scoring of uptake grade and semiquantitative region of interest analysis of the uptake ratio using the thoracic spine as a reference.
Results: Ga scans were positive in 23 of the 24 patients (95.8%) with PTB and in 12 of the 17 patients (70.6%) with pulmonary NTM infection. Twenty patients with active PTB had moderate or intense visual Ga uptake grade, whereas only three patients with pulmonary NTM infection had moderate visual Ga uptake grade. The semiquantitative pulmonary Ga uptake ratios in patients with active PTB and NTM infection were 1.17 ± 0.28 (range: 0.77-1.86) and 0.79 ± 0.12 (range: 0.60-1.03), respectively. The Ga uptake grade and ratio of active PTB were both significantly higher than NTM infection (both P < 0.001). In the receiver operating characteristic curve analysis for predicting active PTB, the area under the curves of Ga uptake grade and ratio were 0.90 ± 0.05 and 0.93 ± 0.04, respectively (both P < 0.001).
Conclusion: The inflammatory activity of active PTB is significantly higher than that of pulmonary NTM infection in non-HIV-infected patients. Ga uptake grade and ratio could be used to predict active PTB in acid-fast bacilli smear-positive patients.