Our research findings show the diagnostic utility of both GeneXpert and TB-LAMP in The Gambia

The paper titled Comparison of TB-LAMP, GeneXpert MTB/RIF and culture for diagnosis of pulmonary tuberculosis (TB) in The Gambia published on Science Direct, was selected as one of the top papers to mark World Tuberculosis day 2017.

The diagnosis of TB remains difficult, particularly in resource-limited settings. The development of nucleic acid-based tests for detection of Mycobacterium tuberculosis complex (MTBC) has significantly increased sensitivity compared to conventional smear microscopy and provides results within a matter of hours compared to weeks for the current gold-standard, liquid culture.

Side-by-side comparison of mycobacterial detection assays on sputum samples

Side-by-side comparison of mycobacterial detection assays on sputum samples

Our research which aimed to determine the use of a novel TB diagnostic test in a laboratory setting showed that TB Loop-Mediated Amplification (TB-LAMP) was comparable to GeneXpert, but required less infrastructure. However, unlike GeneXpert, it is unable to detect drug-resistant patterns and therefore would be most suitable as a screening test for new TB cases in peripheral health clinics.

The research was conducted at MRC Unit The Gambia, between December 2013 and June 2014 funded by the Foundation for Innovative Diagnostics (FIND) as part of a larger multi-site study. Samples for the study were collected within MRCG and the peripheral health clinics and sent to the TB diagnostics lab at MRCG for diagnostic testing.

In this study side-by-side comparison of mycobacterial detection assays on sputum samples was performed on 285 subjects presenting with symptoms suggestive of TB in The Gambia and a cross-sectional cohort of 156 confirmed TB patients with a median of 2 months of treatment. A novel assay, TB-LAMP, was compared to smear microscopy, MGIT culture and GeneXpert MTB/RIF for all samples.

When culture was used as the reference standard, an overall sensitivity for TB-LAMP of 99% (95% CI: 94.5–99.8) and specificity of 94% (95% CI: 89.3–96.7) was found. When latent class analysis was performed, TB-LAMP had 98.6% (95% CI: 95.9–100) sensitivity and 99% (95% CI: 98.2–100) specificity compared to 91.1% (95% CI: 86.1–96) sensitivity and 100% (95% CI: 98.2–100) specificity for MGIT culture. GeneXpert had the highest sensitivity 99.1% (95% CI: 97.1–100) but the lowest specificity 96% (95% CI: 92.6–98.3). Both TB-LAMP and GeneXpert showed high sensitivity and specificity regardless of age or strain of infection.

Read more about the findings on Science Direct at http://www.sciencedirect.com/science/article/pii/S016344531500403X

Acknowledgements
We thank all study participants, TB diagnostic laboratory staff and TB clinic staff.

Authors
Adama L. Bojang, Francis S. Mendy, Leopold D. Tientcheu, Jacob Otu, Martin Antonio, Beate Kampmann, Schadrac Agbla, Jayne S. Sutherland