Objective: Gallium-67 scintigraphy is more sensitive than chest radiography in a single concurrent detection of pulmonary tuberculosis (TB). As for inflammation, the intensity of pulmonary uptake of 67Ga citrate theoretically is a function of the inflammation level in the lung. To maximize clinical applicability of 67Ga scintigraphy in the evaluation of pulmonary TB, we prospectively assessed serial qualitative associations between intensity of the uptake of 67Ga citrate and the severity of lung inflammation, reflected by the burden of Mycobacterium tuberculosis in the sputum of patients undergoing anti-TB chemotherapy.
Subjects and methods: Each enrolled patient had chest radiographic, microbiologic, 67Ga imaging, and semiquantitation of sputum acid-fast bacillus (AFB) assessments before and at the third and sixth months after receiving anti-TB chemotherapy. The burden of pulmonary M. tuberculosis (presumably, in proportion to the semiquantitation of AFB in sputum) and the intensity of 67Ga citrate uptake in the lung at each synchronized assessment were regarded as a paired variable. Odds ratios were obtained from odds (derived using generalized estimating equations) in favor of higher pulmonary 67Ga uptake in differing scores of semiquantitation of sputum AFB. Linear trend for pulmonary 67Ga citrate uptake corresponding to varied pulmonary M. tuberculosis burdens was assessed using contrast analysis of their odds ratios.
Results: Thirty patients (24 men and six women) with pulmonary TB were enrolled. Eighty-six paired semiquantitations of sputum AFB-67Ga-scintigraphic studies were collected. Twenty-six patients were cured of their pulmonary TB. The pulmonary 67Ga uptake increased in proportion to the higher score of semiquantitation of sputum AFB (p = 0.009, for trend).
Conclusion: In patients with pulmonary TB, the higher the burden of M. tuberculosis in the lung, the higher the intensity of pulmonary 67Ga citrate uptake. Serial 67Ga-scintigraphy examinations are helpful in evaluations of the effectiveness of anti-TB therapy when assessments based on chest radiography are difficult.