Abstract
BackgroundHundreds of studies have evaluated the diagnostic accuracy of nucleic-acid amplification tests (NAATs) for tuberculosis (TB). Commercial tests have been shown to give more consistent results than in-house assays. Previous meta-analyses have found high specificity but low and highly variable estimates of sensitivity. However, reasons for variability in study results have not been adequately explored. We performed a meta-analysis on the accuracy of commercial NAATs to diagnose pulmonary TB and meta-regression to identify factors that are associated with higher accuracy.Methodology/Principal FindingsWe identified 2948 citations from searching the literature. We found 402 articles that met our eligibility criteria. In the final analysis, 125 separate studies from 105 articles that reported NAAT results from respiratory specimens were included. The pooled sensitivity was 0.85 (range 0.36–1.00) and the pooled specificity was 0.97 (range 0.54–1.00). However, both measures were significantly heterogeneous (p<.001). We performed subgroup and meta-regression analyses to identify sources of heterogeneity. Even after stratifying by type of commercial test, we could not account for the variability. In the meta-regression, the threshold effect was significant (p = .01) and the use of other respiratory specimens besides sputum was associated with higher accuracy.Conclusions/SignificanceThe sensitivity and specificity estimates for commercial NAATs in respiratory specimens were highly variable, with sensitivity lower and more inconsistent than specificity. Thus, summary measures of diagnostic accuracy are not clinically meaningful. The use of different cut-off values and the use of specimens other than sputum could explain some of the observed heterogeneity. Based on these observations, commercial NAATs alone cannot be recommended to replace conventional tests for diagnosing pulmonary TB. Improvements in diagnostic accuracy, particularly sensitivity, need to be made in order for this expensive technology to be worthwhile and beneficial in low-resource countries.
Highlights
Tuberculosis (TB) is a major global health problem
Most of the studies (96%) collected both smearpositive and smear-negative specimens, and 84% compared nucleic-acid amplification tests (NAATs) results to culture as the reference standard
Lack of rapid and accurate diagnostics for TB has been a major concern for global TB control
Summary
Tuberculosis (TB) is a major global health problem. Each year, 8 to 9 million people develop disease, and 2 million die [1]. Nucleic acid amplification tests (NAATs), which can give results in 3– 6 hours, have been developed to address these issues [9]. Hundreds of studies have evaluated the diagnostic accuracy of nucleic-acid amplification tests (NAATs) for tuberculosis (TB). We performed a meta-analysis on the accuracy of commercial NAATs to diagnose pulmonary TB and meta-regression to identify factors that are associated with higher accuracy. 125 separate studies from 105 articles that reported NAAT results from respiratory specimens were included. The use of different cut-off values and the use of specimens other than sputum could explain some of the observed heterogeneity Based on these observations, commercial NAATs alone cannot be recommended to replace conventional tests for diagnosing pulmonary TB. Improvements in diagnostic accuracy, sensitivity, need to be made in order for this expensive technology to be worthwhile and beneficial in low-resource countries
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