Journal List > Tuberc Respir Dis > v.62(5) > 1001087

Lee: CT Findings Related to Negative Results of Sputum Smear in Patients with Active Pulmonary Tuberculosis having Multiple Cavities

Abstract

Background

This study evaluated which CT findings could be used to predict the negative results of a sputum smear in patients with active pulmonary tuberculosis and multiple cavities.

Methods

Thirty-eight patients with active pulmonary tuberculosis and multiple cavities on CT were classified into 2 groups: smear-positive (n = 30) and -negative (n = 8). The CT findings were reviewed retrospectively. The maximum internal diameter of the largest cavity, the number of the cavities and lobes with cavities, and the characteristics of the associated findings such as consolidation, ground glass opacity, micronodules and nodule were accessed. The number of cavities above 20 mm in the maximum internal diameter and a necrotizing pneumonia-like pattern were also evaluated.

Result

The maximum internal diameter and number of cavities was 32.23 ± 17.66 mm and 15.50 ± 11.12 mm (p = 0.0042), and 5.53 ± 3.17 and 2.43 ± 1.13 (p = 0.0002) in the smear-positive and -negative group, respectively. Three or more cavities were observed at 76.7% and 12.5% in the smear-positive and -negative group, respectively (p < 0.005). There were 2.00 ± 1.34 and 0.25 ± 0.46 (p = 0.001), and 1.5 ± 1.50 and 0.38 ± 0.52 (p = 0.0016) lobes with consolidation and ground glass opacity in the smear-positive and -negative group, respectively. A necrotizing pneumonia-like pattern was observed in 43.3% of the smear-positive group only. The other findings were similar in both two groups. The sensitivity, specificity, positive and negative predictive value for the presence of at least a finding of consolidation, more than 3 cavities or the largest cavity > 20 mm in the maximum internal diameter were 100%, 62.5%, 90.9%, and 100%, respectively.

Conclusion

Two cavities 20 mm or less in the maximum internal diameter without consolidation on CT might be associated with a negative result of the sputum smear in patients with active pulmonary tuberculosis and multiple cavities.

Figures and Tables

Figure 1
CT images of a 65-year-old man among the sputum smear-negative group A. CT scan at the level of left upper lobe apex shows a cavity (7 mm in maximum internal diameter) (arrows). B. CT scan at the level of right upper lobe shows a cavity (6 mm in maximum internal diameter) (arrows). The rest CT scans of this patient showed no evidence of consolidation or another cavity.
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Table 1
Frequencies of CT findings in each group
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Values in parentheses are percentages.

*means maximum internal diameter.

Table 2
Mean number of pulmonary lobes involving consolidation, ground-glass opacities, micronodules, and nodules in each group
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Table 3
Sensitivity, specificity, positive predictive value and negative predictive value of each CT finding
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PPV: positive predictive value; NPV: negative predictive value.

*means maximum internal diameter.

Table 4
CT findings showing statistically significant differences between two groups
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Table 5
Clinical, laboratory and CT characteristics in 8 patients of group 2
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No means number.

NA means not available.

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