The current evidence on diagnostic accuracy of commercial based nucleic acid amplification tests for the diagnosis of pulmonary tuberculosis

Stefania Greco ^1*, Enrico Girardi ², Assunta Navarra ³ and Cesare Saltini ⁴

¹ Azienda Ospedaliera San Camillo-Forlanini, Roma, Italy
² INMI Lazzaro Spallanzani, Roma, Italy
³ INMI Lazzaro Spallanzani, Italy
⁴ Dip.to di Medicina Interna, Università di Tor Vergata, Italy

^* To whom correspondence should be addressed. E-mail: stgreco{at}scamilloforlanini.rm.it.

Accepted 18 May 2006

Abstract

Background: Even if commercial nucleic acid amplification tests (NAATs) have become the most frequently used molecular tests for laboratory diagnosis of pulmonary tuberculosis (TB), published studies report variable estimates of their diagnostic accuracy. We analyzed the accuracy of commercial NAATs for pulmonary TB diagnosis separately on smear-positive and smear-negative respiratory samples, using culture as reference standard.

Methods: English-language studies reporting data sufficient for calculating sensitivity and specificity of commercial NAATs on smear-positive and/or smear-negative respiratory samples were included. Meta-regression was used to analyse associations with reference test quality, TB prevalence, sample and test type. Predictive values for different levels of pre-test probability were quantified using Bayes' approach.

Results: Sixty-three journal articles, published between 1995 and 2004, met the inclusion criteria. Median sensitivity and specificity were 0,97 and 0,9 among smear positive and 0,66 and 0,98 among smear negative samples. The number of culture media used as reference test, the inclusion of bronchial samples and the TB prevalence were found to influence the reported accuracy. The test type had no impact on diagnostic odds ratio, but seemed to be correlated with sensitivity or specificity, probably via a threshold effect.

Conclusions: Currently, commercial NAATs can be confidently used 1) to exclude TB in patients with smear-positive samples in which environmental mycobacteria infection is suspected and 2) to confirm TB in a proportion of smear-negative cases. The methodological characteristics of primary studies determine considerable and meaningful changes in the reported diagnostic accuracy.

Keywords: diagnostic tests, meta-analysis, nucleic acid amplification techniques, pulmonary tuberculosis

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