The rapid diagnosis of smear-negative pulmonary tuberculosis: A cost-effectiveness analysis

Publication Type

Journal Article

Publication Date

12-2000

Abstract

The rapid diagnosis of smear-negative pulmonary tuberculosis: A cost-effectiveness analysis LIM TK, CHERIAN J, POH KL, LEONG TY. Respirology 2000; 5: 403-409 Objective: The prompt diagnosis of smear-negative pulmonary tuberculosis (PTB) is a clinical challenge. It may be achieved by a number of tests which have varying accuracies, costs and degrees of invasiveness. The objective of this study was to compare the cost-effectiveness of clinical judgement (empirical), the Roche Cobas amplicor assay for Mycobacterium tuberculosis (amplicor), acid-fast staining of bronchoalveolar lavage specimens (BAL), nucleic acid amplification tests of bronchoalveloar lavage specimens for M. tuberculosis (BAL + NAA), computed tomography (CT) and amplicor assay followed by BAL. Methodology: The range of predictive values of the various strategies were derived from published data and a new study of 441 consecutive adult patients with suspected smear-negative PTB prospectively stratified into three pretest risk groups: Low, intermediate and high. The cost-effectiveness was evaluated with a decision tree model (DATA™ software). Results: The incidence of PTB was 5.7% (4% culture positive) for the whole group, 95% in the highrisk group, 0.9% in the low-risk group and 3.4% in the intermediate-risk group. The sensitivity of the empirical approach was 49% and of the amplicor assay was 44%. Patient outcomes were expressed as life expectancy for the base case of a 58-year-old man with a pretest probability of 5.7%. At this low pretest risk the differences in life expectancies between tests was < 0.1 years and the empirical approach incurred the lowest cost. Sensitivity analysis at increasing pretest risks showed better life expectancies (∼ 1 years) for CT scan and test combinations than empirical and amplicor for additional costs of US$243-US$309. Bronchoalveolar lavage had the worst overall cost-effectiveness. Conclusions: We conclude that the pretest risk of active PTB was a key determinant of test utility; that the AMPLICOR assay was comparable to clinical judgement; that BAL was the least useful test; and that with increasing risks, CT scan and test combinations performed better. Further studies are needed to better define patients with intermediate risk for PTB and to directly compare the cost-effectiveness of more sensitive nucleic acid amplification tests such as the enhanced Gen Probe, CT scan and test combinations/sequences in these patients.

Keywords

Amplicor, Bronchoscopy, Computed tomography, Pulmonary tuberculosis, Smear negative

Discipline

Databases and Information Systems

Publication

Respirology

Volume

5

Issue

4

First Page

403

Last Page

409

ISSN

1323-7799

Identifier

10.1046/j.1440-1843.2000.00284.x

Publisher

Wiley: 12 months

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