The relation between CT findings and sputum microbiology studies in active pulmonary tuberculosis

To evaluate whether CT findings suggesting active pulmonary tuberculosis correlate with sputum microbiological studies, and to determine whether CT could predict infectivity.

Total 108 patients with active pulmonary tuberculosis were enrolled. We reviewed CT findings and sputum microbiological studies. Then, we analyzed the statistical difference in CT findings between the positive and negative groups of each sputum microbiological study (AFB smear, PCR, and culture). Also, we divided the patients into five groups according to sputum AFB smear grade and analyzed linear trends of CT findings between the five groups.

Both frequencies and extents of centrilobular micronodules (63% vs 38%, p=0.011 for frequency; 1.6 ± 1.6 vs 0.6 ± 1.1, p=0.001 for extent), tree-in-bud opacities (63% vs 33%, p=0.002; 1.6 ± 1.6 vs 0.5 ± 0.9, p<0.001, respectively), consolidation (98% vs 81%, p=0.003; 2.7 ± 1.5 vs 1.3 ± 1.1, p<0.001, respectively), and cavitation (86% vs 33%, p<0.001; 1.5 ± 1.2 vs 0.4 ± 0.7, p<0.001, respectively), were significantly increased in the sputum AFB-positive group than in the negative group. These four CT findings were increase in frequency and extent in the sputum PCR-positive group with or without statistical significance. They did not show significant differences between the sputum culture-positive and negative groups. As the AFB smear grade increased, frequencies and extents of centrilobular micronodules, tree-in-bud, consolidation, and cavitation also increased.

CT features representing active tuberculosis-centrilobular nodules, tree-in-bud, consolidation, and, cavitation-strongly correlate with the positivity and grading of AFB smear.