Utility of high-resolution computed tomography for predicting risk of sputum smear-negative pulmonary tuberculosis

doi:10.1016/j.ejrad.2008.12.009

European Journal of Radiology

Volume 73, Issue 3, March 2010, Pages 545-550

https://doi.org/10.1016/j.ejrad.2008.12.009 Get rights and content

Abstract

Background

To diagnose sputum smear-negative pulmonary tuberculosis (PTB) is difficult and the ability of high-resolution computed tomography (HRCT) for diagnosing PTB has remained unclear in the sputum smear-negative setting. We retrospectively investigated whether or not this imaging modality can predict risk for sputum smear-negative PTB.

Methods

We used HRCT to examine the findings of 116 patients with suspected PTB despite negative sputum smears for acid-fast bacilli (AFB). We investigated their clinical features and HRCT-findings to predict the risk for PTB by multivariate analysis and a combination of HRCT findings by stepwise regression analysis. We then designed provisional HRCT diagnostic criteria based on these results to rank the risk of PTB and blinded observers assessed the validity and reliability of these criteria.

Results

A positive tuberculin skin test alone among clinical laboratory findings was significantly associated with an increase of risk of PTB. Multivariate regression analysis showed that large nodules, tree-in-bud appearance, lobular consolidation and the main lesion being located in S1, S2, and S6 were significantly associated with an increased risk of PTB. Stepwise regression analysis showed that coexistence of the above 4 factors was most significantly associated with an increase in the risk for PTB. Ranking of the results using our HRCT diagnostic criteria by blinded observers revealed good utility and agreement for predicting PTB risk.

Conclusions

Even in the sputum smear-negative setting, HRCT can predict the risk of PTB with good reproducibility and can select patients having a high probability of PTB.

Introduction

The sensitivity of sputum smear examination for acid-fast bacilli (AFB) is poor [1], therefore, rapid and accurate diagnosis of smear-negative pulmonary tuberculosis (TB) is warranted. To culture clinical specimens for AFB requires several weeks and radiographic diagnosis is not very accurate [2], [3]. Although the polymerase chain reaction (PCR) can rapidly diagnose pulmonary tuberculosis (PTB), sensitivity is low [4], [5], [6]. A high probability of PTB needs to be identified among sputum smear-negative findings without missing patients who do indeed have PTB.

The characteristic findings of high-resolution CT (HRCT) in terms of PTB have been reported [7], [8], [9] and the accuracy of HRCT for diagnosing PTB is reportedly high [9]. However, these characteristics were determined with respect to other pulmonary disorders [10], [11], [12], [13], [14] and characteristic findings of PTB by HRCT have not been established. In addition, the effectiveness of HRCT has not been investigated in the sputum smear-negative setting. Furthermore, we considered that HRCT abnormalities should be interpreted from a combination of HRCT findings, because PTB is difficult to diagnose by a single HRCT finding in most cases and though HRCT is useful for predicting risk for PTB, it is not a gold standard.

In this study, we retrospectively investigated the findings on HRCT and a combination of those significantly increasing the risk of PTB in patients suspected of having sputum smear-negative PTB. Furthermore, we provisionally designed HRCT criteria with which to predict the risk for PTB using multivariate analysis to test the reliability and validity of HRCT diagnosis.

Section snippets

Methods

We studied 116 patients who presented at the 2 institutions where this study was conducted between April 2000 and March 2005. All were sputum smear-negative for AFB twice at least or did not expectorate sputum and had pulmonary infiltrates of unknown origin. Their HRCT findings indicated suspected PTB and they were also examined by PCR in sputum or bronchoscopic specimens.

We routinely conduct sputum smear and culture for AFB and chest CT examinations for all patients with active pulmonary

Results

Of the 116 patients with suspected PTB, a positive tuberculin skin test result alone among clinical and laboratory findings was significantly associated with an increased risk for PTB. No other findings were significantly associated with an increase in the risk for PTB (Table 2).

Table 3 shows the results of multivariate regression analysis of the relationship between PTB and HRCT findings. Large nodules, tree-in-bud appearance, lobular consolidation, and location of the main lesion in S1, S2,

Discussion

All of the patients with PTB in this study had relatively mild disease activity and their sputum smears were negative for AFB. Although the clinical and laboratory findings between PTB and other diseases rarely differ significantly, HRCT findings can differentiate between them. The present study showed that large nodules, tree-in-bud appearance, lobular consolidation, and location of the main lesion in S1, S2, and S6 on HRCT were significantly associated, and a combination of these 4 factors

Conclusions

The main role of HRCT for diagnosing PTB is the selection of probable or highly suspected PTB among patients with pulmonary infiltrates of unknown origin and with negative sputum smears. This is because HRCT can predict the risk of PTB by depicting characteristic findings for PTB even in the sputum smear-negative setting. It can also exclude other diseases and select patients that are difficult to diagnose with a pretest probability of PTB while missing few of those that are clearly positive

Conflicts of interest

No financial or other potential conflicts of interest exist.

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Utility of high-resolution computed tomography for predicting risk of sputum smear-negative pulmonary tuberculosis

Abstract

Background

Methods

Results

Conclusions

Introduction

Section snippets

Methods

Results

Discussion

Conclusions

Conflicts of interest

Chest

Chest

New tools for the diagnosis of tuberculosis: the perspective of developing countries

Int J Tuberc Lung Dis

Update: the radiographic features of pulmonary tuberculosis

AJR

Presumptive diagnosis and treatment of pulmonary tuberculosis based on radiographic findings

Am Rev Respir Dis

Relationship between estimated pretest probability and accuracy of automated mycobacterium tuberculosis assay in smear-negative pulmonary tuberculosis

Chest

Diagnosis of pulmonary tuberculosis using PCR assays on sputum collected within 24 hours of hospital admission

Am J Respir Crit Care Med

Pulmonary tuberculosis: CT findings—early active disease and sequential change with antituberculous therapy

Radiology