Tuberc Respir Dis.  2007 May;62(5):374-381.

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

• Lee HY

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.

Keyword

Computed tomography; Sputum smear; Pulmonary tuberculosis

MeSH Terms

Glass
Humans
Retrospective Studies
Sputum*
Tuberculosis, Pulmonary*

Figure

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  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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