800 Assessing the efficacy of GeneXpert in diagnosing TB in a paediatric population

Abstract

<h3>Aims</h3> GeneXpert is a molecular TB test which detects the presence of TB DNA in samples such as sputum and can publish results in less than 2 hours. It can also be used to detect resistance to the drug Rifampicin, important in the management of TB. In this study, a retrospective audit of the paediatric TB cases from a tertiary paediatric unit was carried out, looking at the sensitivity of GeneXpert in diagnosing TB in this population using sputum and lymph node samples. <h3>Methods</h3> This study considered 77 patients with active paediatric TB who were diagnosed between January 2011 and March 2021. Data was collected on these patients using electronic records and then entered on a pro forma. The sensitivity of GeneXpert in diagnosing both pulmonary and extra-pulmonary TB in these patients was recorded and analysed. Extra-pulmonary TB in this case includes CNS and lymph node TB. <h3>Results</h3> GeneXpert exhibited an overall sensitivity of 55% (11/20) when all sample types are amalgamated (figure 1). Sputum samples exhibited a sensitivity of 54% (7/13) for pulmonary TB and 100% (1/1) for extra-pulmonary TB. The lymph nodes samples gave a 100% sensitivity for pulmonary (2/2) as well as extra-pulmonary (3/3) TB. It was also noted that only 26% (20/77) of TB patients in this audit were tested using GeneXpert. <h3>Conclusion</h3> Based on the above results, GeneXpert has a greater sensitivity for extra-pulmonary samples, with lymph node being the most reliable sample type. The results for GeneXpert in this audit are lower than have been recorded in past studies, with much higher sensitivity rates being recorded previously.¹ However, it must be noted that the utilisation of GeneXpert in our hospital was relatively low and more patients should be tested using this method in the future to fully elucidate the efficacy of this test.^2,3 Furthermore, the sensitivity of this test compares favourably to that of sputum cultures, stool cultures and gastric aspirate samples from this audit, indicating its potential effectiveness at diagnosing TB compared to the current standard methods as well as a much quicker turnaround to gaining test results and drug sensitivities than these methods. <h3>References</h3> Steingart KR, Schiller I, Horne DJ, Pai M, Boehme CC, Dendukuri N., ‘Xpert(R) MTB/RIF assay for pulmonary tuberculosis and rifampicin resistance in adults.’, <i>Cochrane Database Syst Rev</i>. 2014. Giang DC, Duong TN, Ha DTM, <i>et al</i>. Prospective evaluation of GeneXpert for the diagnosis of HIV- negative paediatric TB cases. <i>BMC Infect Dis.</i> 2015;<b>15</b>(7). Moussa, Husseiny SH, <i>et al</i>. Evaluation of GeneXpert MTB/RIF assay for direct diagnosis of pulmonary tuberculosis. <i>Saudi medical journal</i> 2016;<b>37</b>(10).