Abstract
BackgroundTuberculosis rapid molecular assays, including GeneXpert MTB/RIF® and Loopamp MTBC Detection Kit®, are highly sensitive and specific. Such performance does not automatically translate in improved disease control and highly depends on their use, local epidemiology and the diagnostic algorithms they’re implemented within. We evaluate the performance of both assays and assess their impact on additional cases notification when implemented within WHO recommended tuberculosis diagnostic algorithms in Madagascar.MethodsFive hundred forty eight presumptive pulmonary tuberculosis patients were prospectively recruited between November 2013 and December 2014 in Antananarivo, Madagascar, a high TB incidence sub-Saharan African urban setting. Both molecular assays were evaluated as first line or add-on testing following negative smear microscopy. Based on locally defined assay performance characteristics we measure the impact of both assays and WHO-recommended diagnostic algorithms on additional tuberculosis case notifications.ResultsHigh sensitivity and specificity was confirmed for both GeneXpert MTB/RIF® (86.6% (95% CI 81.1–90.7%) and 97.4% (95% CI 94.9–98.8%)) and Loopamp MTBC Detection Kit® (84.6% (95% CI 78.9–89.0%) and 98.4% (95% CI 96.2–99.4%)). Implementation of GeneXpert MTB/RIF® and Loopamp MTBC Detection Kit® increased tuberculosis diagnostic algorithms sensitivity from 73.6% (95% CI 67.1–79.3%) up to 88.1% (95% CI 82.8–91.9%). This increase was highest when molecular assays were used as add-on testing following negative smear microscopy. As add-on testing, GeneXpert MTB/RIF® and Loopamp MTBC Detection Kit® respectively improved case detection by 23.8 and 21.2% (p < 0.05).ConclusionIncluding GeneXpert MTB/RIF® or Loopamp MTBC Detection Kit® molecular assays for TB detection on sputum samples from presumptive TB cases can significantly increase case notification in TB diagnostic centers. The TB case detection rate is further increased when those tests are use as second-line follow-on testing following negative smear microscopy results. A country wide scale-up and digital integration of molecular-based TB diagnosis assays shows promises for TB control in Madagascar.
Highlights
Tuberculosis rapid molecular assays, including GeneXpert MTB/RIF® and Loopamp MTBC Detection Kit®, are highly sensitive and specific
To bypass the inconvenient delays and biosecurity requirements associated with bacterial culture, GeneXpert MTB/RIF® (Cepheid; USA) polymerase chain reaction (PCR) and Loopamp MTBC Detection Kit® (Eiken Chemical Co; Japan) loop-mediated isothermal amplification (LAMP)based molecular assays were developed, validated on direct sputum samples and endorsed by the World Health Organization (WHO) respectively in 2013 and 2016 [2, 3]
The objective of this study was to evaluate the diagnostic performance of GeneXpert MTB/RIF® and Loopamp MTBC Detection Kit® assays and assess their impact on case detection when implemented as stand-alone assays for first-line testing or as a followon test following negative sputum smear microscopy testing
Summary
Tuberculosis rapid molecular assays, including GeneXpert MTB/RIF® and Loopamp MTBC Detection Kit®, are highly sensitive and specific. To bypass the inconvenient delays and biosecurity requirements associated with bacterial culture, GeneXpert MTB/RIF® (Cepheid; USA) polymerase chain reaction (PCR) and Loopamp MTBC Detection Kit® (Eiken Chemical Co; Japan) loop-mediated isothermal amplification (LAMP)based molecular assays were developed, validated on direct sputum samples and endorsed by the World Health Organization (WHO) respectively in 2013 and 2016 [2, 3]. Those assays can either be used as first-line testing in place of sputum smear microscopy or as a follow-on test in adults with symptoms of pulmonary TB but testing negative on smear microscopy [4, 5]. Assays impact on case notifications can vary with context-specific factors including, disease prevalence, population age distribution, HIV rates and implemented diagnosis algorithms
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