Evaluation of Luminex xTAG Gastrointestinal Pathogen Panel Assay for Detection of Multiple Diarrheal Pathogens in Fecal Samples in Vietnam

Abstract

Diarrheal disease is a complex syndrome that remains a leading cause of global childhood morbidity and mortality. The diagnosis of enteric pathogens in a timely and precise manner is important for making treatment decisions and informing public health policy, but accurate diagnosis is a major challenge in industrializing countries. Multiplex molecular diagnostic techniques may represent a significant improvement over classical approaches. We evaluated the Luminex xTAG gastrointestinal pathogen panel (GPP) assay for the detection of common enteric bacterial and viral pathogens in Vietnam. Microbiological culture and real-time PCR were used as gold standards. The tests were performed on 479 stool samples collected from people admitted to the hospital for diarrheal disease throughout Vietnam. Sensitivity and specificity were calculated for the xTAG GPP for the seven principal diarrheal etiologies. The sensitivity and specificity for the xTAG GPP were >88% for Shigella spp., Campylobacter spp., rotavirus, norovirus genotype 1/2 (GI/GII), and adenovirus compared to those of microbiological culture and/or real-time PCR. However, the specificity was low (∼60%) for Salmonella species. Additionally, a number of important pathogens that are not identified in routine hospital procedures in this setting, such as Cryptosporidium spp. and Clostridium difficile, were detected with the GPP. The use of the Luminex xTAG GPP for the detection of enteric pathogens in settings, like Vietnam, would dramatically improve the diagnostic accuracy and capacity of hospital laboratories, allowing for timely and appropriate therapy decisions and a wider understanding of the epidemiology of pathogens associated with severe diarrheal disease in low-resource settings.

Multiplex tests to identify gastrointestinal bacteria, viruses and parasites in people with suspected infectious gastroenteritis: a systematic review and economic analysis

“…Ten studies [20][21][22][23][24][25][26][27]29,30 reported results of association between the comparator and the GPP test in sufficient detail by pathogen to allow the construction of 2 × 2 tables by pathogen. These studies are further characterised in Table 7 and contributed data to the meta-analysis in Pathogen-level positive and negative agreement.…”

“…Two studies tested all samples with comparator methods, but these were not equivalent to conventional methods of the PHE algorithm. 20,25 In three studies, 22,24,30 samples had received all conventional methods, but the studies only looked at a limited number of pathogens, and Gu et al 26 constructed a comparator for which conventional methods were undertaken according to the physician's judgement, but additional testing for astrovirus, norovirus and sapovirus was undertaken for all samples.…”

“…Use of GPP testing showed less variation across studies; 2 × 2 data were available from nine studies [21][22][23][24][25][26][27]29,30 for xTAG and from two studies 20,26 for FilmArray. Of interest is the batching method reported by Halligan et al, 27 who batched samples for DNA extraction at 16.00 Monday-Thursday and subsequent analysis of samples the following morning with results available at 15.00.…”

“…Studies retrospectively included samples with confirmed gastroenteritis and negative controls 30 or prospectively included samples from patients with suspected gastroenteritis. [20][21][22][23][24][25][26][27]29 Comparator and GPP tests were both undertaken at the study site(s) in seven studies, [22][23][24][25][26][27]29 whereas one study sent the samples to reference laboratories for conventional testing, 30 one study sent the samples to Luminex for GPP testing 21 and one study sent the samples to BioFire for comparator testing. 20 Verification was undertaken on all discrepant samples by four studies, 20 29 The remaining three studies, 24,26,27 which did not undertake verification, assumed either that the comparator methods are the reference standard to calculate sensitivity and specificity 24,26 or assumed that the GPP assay is correct and did not calculate sensitivity and specificity because of the lack of a resolving assay.…”

“…Seven studies 19,22,26,27,29,35,39 reported the setting sufficiently to allow judgement on the origin of the infection (hospital vs. community). The majority of studies 11,12,20,21,[23][24][25]28,[30][31][32][33][34][36][37][38] reported recruitment of hospitalised patients, for which a mixed population should be assumed (in terms of origin of infection) as it is unclear at what point in time during hospitalisation each infection occurred. Only one study was identified as a community study, set in Côte d'Ivoire.…”