Research Article: Diagnostic accuracy of the loop-mediated isothermal amplification assay for extrapulmonary tuberculosis: A meta-analysis

Date Published: June 26, 2018

Publisher: Public Library of Science

Author(s): Guocan Yu, Yanqin Shen, Fangming Zhong, Bo Ye, Jun Yang, Gang Chen, Sanjai Kumar.


Loop-mediated isothermal amplification (LAMP) is used to detect pulmonary tuberculosis (PTB); however, the diagnostic accuracy of the LAMP assay for extrapulmonary tuberculosis (EPTB) is unclear. We performed a meta-analysis to evaluate the performance of LAMP in the detection of EPTB.

We searched PubMed, EMBASE, the Cochrane Library, China National Knowledge Infrastructure (CNKI), and the Wanfang database for studies published before Sep 16, 2017. We reviewed studies and compared the performance of LAMP with that of a composite reference standard (CRS) and culture for clinically suspected EPTB. We used a bivariate random-effects model to perform meta-analyses and used meta-regression and subgroup analysis to analyze sources of heterogeneity.

Fourteen articles including 24 independent studies (16 compared LAMP to CRS, 8 to culture) of EPTB were identified. LAMP showed a pooled sensitivity of 77% (95% confidence interval (CI) 68–85), specificity of 99% (95% CI 96–100), and area under SROC curves (AUC) of 0.96 (95% CI 0.94–0.97) against CRS. It showed a pooled sensitivity of 93% (95% CI 88–96), specificity of 77% (95% CI 64–86), and AUC of 0.94 (95% CI 0.92–0.96) against culture. The pooled sensitivity, specificity, and AUC of MPB64 LAMP were 86% (95% CI 86–86), 100% (95% CI 100–100), and 0.97 (95% CI 0.95–0.98), respectively, and those of IS6110 LAMP were 75% (95% CI 64–84), 99% (95% CI 90–100), and 0.91 (95% CI 0.88–0.93), respectively, compared with CRS.

These results suggest good diagnostic efficacy of LAMP in the detection of EPTB. Additionally, the diagnostic efficacy of MPB64 LAMP was superior to that of IS6110 LAMP.

Partial Text

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (MTB) and is one of the most serious challenges to public health [1]. The most common site of tuberculosis infection is the lung, but bacteria can also spread to extrapulmonary sites, causing extrapulmonary tuberculosis (EPTB). EPTB accounts for approximately 22% of total TB cases [2]. Diagnosis of EPTB is very challenging, because specimens of EPTB are not as easy to obtain by noninvasive methods as are sputum samples. Invasive procedures requiring special expertise are often required to obtain specimens such as cerebrospinal fluid and pleural effusion. Additionally, culture of EPTB specimens has low sensitivity. Biopsy along with histopathological examination and culture is required to diagnose EPTB.

We followed the standard guidelines to perform this meta-analysis [4–6].

Timely and accurate diagnosis of tuberculosis is very important for effective management of the disease and prevention of infection in the community, particularly in areas with high burdens tuberculosis. Conventional diagnostic methods, such as smears and culture, are time-consuming and not very sensitive.

In this meta-analysis, we observed that the pooled sensitivity and specificity of LAMP for the detection of EPTB were 77% and 93%, respectively, when compared with a CRS, and 99% and 77%, respectively, when compared with culture. Depending on the assessment of AUC, LAMP showed good diagnostic efficacy. We also found that the diagnostic efficacy of LAMP tests varied according to different target genes; the diagnostic efficacy of MPB64 LAMP was better than that of IS6110 LAMP. The diagnostic accuracy of LAMP for different samples could not be effectively assessed, as the number of studies using different sample types was limited. Additionally, an in-house LAMP assay might be superior to the Loopamp MTBC assay. Because of its low cost, LAMP could be useful in the diagnosis of EPTB, particularly in areas where financial resources are limited and drug-resistant MTB is not prevalent.




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