Xpert® MTB/RIF assay testing on stool for the diagnosis of paediatric pulmonary TB in Tanzania

A multicountry evaluation of the Xpert MTB/RIF assay for the diagnosis of intrathoracic tuberculosis in children using alternative specimens (nasopharyngeal aspirate and stool): A prospective cohort study conducted in Madagascar, Ivory Coast and Cameroon (TB KIDS project)

OBJECTIVES

Tuberculosis (TB) diagnosis in children remains challenging due to the paucibacillary nature of specimens and the difficulty in obtaining suitable samples. The use of alternative samples like nasopharyngeal aspirate (NPA) and stools, alongside Xpert MTB/RIF testing, offers promising improvements. This study aimed to assess the diagnostic performance of the Xpert MTB/RIF test on NPA and stool samples for detecting intrathoracic TB in children from Madagascar, Cameroon, and Ivory Coast.

METHODS

Children under 15 years with suspected intrathoracic TB were enrolled in hospitals in these countries' capitals. Samples for analysis included standard specimens (gastric aspirate or sputum), NPA, stools, with additional HIV serology, tuberculin skin test tests, and chest X-rays. We used a composite reference standard to estimate the accuracy of the Xpert MTB/RIF test with alternative samples.

RESULTS

Of 1146 children analyzed, the sensitivity of Xpert MTB/RIF was 58.3% for NPA and 45.5% for stool samples, with a high specificity of more than 95%. The diagnostic performance of Xpert MTB/RIF with alternative samples did not differ according to age group or HIV status.

CONCLUSIONS

The findings support the World Health Organization's recommendation for using Xpert MTB/RIF with alternative samples in childhood TB diagnosis, underscoring its utility across different settings and HIV statuses.

Stool processing methods for Xpert Ultra testing in childhood tuberculosis: A prospective, multi-country accuracy study

Background

Centrifuge-free processing methods support stool Xpert Ultra testing for childhood tuberculosis (TB), but there are limited data on their accuracy, acceptability and usability.

Methods

We conducted a prospective evaluation of stool Xpert Ultra in India, South Africa, and Uganda with three methods: Stool Processing Kit (SPK), Simple One-Step (SOS), and Optimized Sucrose Flotation (OSF). Children <15 years old with presumptive TB had respiratory specimen testing with Xpert Ultra and culture. Stool was tested using Xpert Ultra after processing with each method. We compared the accuracy of each method to a microbiological reference standard (MRS) and a composite reference standard (CRS). We surveyed the laboratory staff to assess acceptability and usability of the methods.

Results

We included 607 children, of whom the median age was 3.5 years (IQR 1.3-7), 48% were female, and 15.5% were HIV positive. Against the MRS, the sensitivities of SPK, SOS and OSF were 36.9% (95% CI 28.6-45.8), 38.6% (95% CI 17.2-51), and 31.3% (95% CI 20.2-44.1), respectively. The specificities of SPK, SOS and OSF were 98.2% (95% CI 96.4-99.3), 97.3% (95% CI 93.7-99.1) and 97.1% (95% CI 93.3-99), respectively. Laboratory staff reported that the methods were acceptable and usable, but SOS was most feasible to implement in a peripheral facility. Sensitivity increased among children who were culture-positive (55-77.3%) and was low (13-16.7%) against the CRS.

Conclusions

Stool processing methods for Xpert Ultra were acceptable, usable, and performed similarly, with highest sensitivity among children with culture-positive TB.

Performance of stool-based molecular tests and processing methods for paediatric tuberculosis diagnosis: a systematic review and meta-analysis

BACKGROUND

There has been a global pursuit to improve the diagnosis of tuberculosis in young children by applying diagnostic methods on accessible biospecimens such as stool. We aimed to conduct a systematic review on the accuracy of stool-based molecular tests for tuberculosis diagnosis in children and to assess the impact of the available pre-processing methods and other design characteristics.

METHODS

In this systematic review and meta-analysis, we evaluated studies in children younger than 16 years with presumptive tuberculosis that were published in English, Spanish, French, and Portuguese from Jan 1, 2000, to May 3, 2024, in MEDLINE, Embase, and Embase Classic, comparing the molecular detection of Mycobacterium tuberculosis DNA in stool with microbiological tests on other samples or a clinical diagnosis. We did not exclude studies based on geographical location, sample size, or study design if they were reporting primary data. Two independent reviewers (LC-C and SM) screened titles, abstracts, and full-text articles for eligibility and extracted data on study characteristics, study population, and diagnostic performance. If information relevant to the main analysis was not reported in the article, the corresponding authors were contacted. Point estimates and 95% CIs were calculated for sensitivity and specificity for each study and for the different molecular tests (Xpert MTB/RIF, Xpert Ultra MTB/RIF [Cepheid, Sunnyvale, CA, USA], and other tests) versus a reference standard (culture only, any bacteriological confirmation, and tuberculosis case definition). Sensitivity and specificity were stratified by the stool processing method. We also quantified the additionality of stool Xpert Ultra tests for tuberculosis bacteriological confirmation. The protocol was registered with PROSPERO, CRD42022341514.

FINDINGS

A total of 4521 records were identified through the database search, one record was identified from an article bibliography, and 67 studies were retained for full-text reading. 39 studies were included in the qualitative synthesis, 35 of which were included in the meta-analyses. When using any bacteriological confirmation from a respiratory sample as the reference standard, stool Xpert sensitivity was 0·60 (95% CI 0·48-0·71), stool Xpert Ultra sensitivity was 0·73 (0·63-0·81), and sensitivity was 0·44 (0·29-0·60) for other in-house molecular methods combined. When using tuberculosis case definition as the reference standard, stool Xpert sensitivity was 0·23 (0·11-0·41), stool Xpert Ultra sensitivity was 0·38 (0·22-0·56), and sensitivity was 0·17 (0·09-0·23) for other in-house molecular methods. The addition of stool Xpert Ultra increased bacteriological confirmation of tuberculosis by 38·6% overall. Further, the utilisation of centrifuge-free simplified methods improved the sensitivity of stool Xpert Ultra when using any bacteriological confirmation as a reference standard (0·77 [0·66-0·85] for centrifuge-free methods vs 0·61 [0·41-0·78] for non-centrifuge-free methods).

INTERPRETATION

This systematic review and meta-analysis supports the use of Xpert Ultra in stool samples as a diagnostic tool for paediatric tuberculosis diagnosis. Stool-based Xpert Ultra can contribute to increase the bacteriological confirmation in this population, even when respiratory specimens are also tested.

FUNDING

The EDCTP2 programme supported by the EU via Stool4TB Project and the European Society of Pediatric Infectious Diseases.

Diagnostic Accuracy of Cartridge Based Nucleic Acid Amplification Test (CBNAAT) in Stool Samples in Pediatric Tuberculosis

OBJECTIVES

To find out the diagnostic accuracy of stool Cartridge-based nucleic acid amplification test (CBNAAT) as an alternate method as compared to CBNAAT in gastric aspirate (GA) samples in pediatric tuberculosis (TB).

METHODS

This cross-sectional study was performed at Department of Pediatrics of a tertiary care hospital. Children aged 0-18 y diagnosed as presumptive tuberculosis were consecutively enrolled. Gastric aspirate and corresponding stool sample was subjected to CBNAAT and its performance was compared in both samples using appropriate statistical tests.

RESULTS

Total 100 patients were enrolled in the study. Diagnostic accuracy of CBNAAT was 81% and 80% in gastric aspirate and stool sample respectively. On comparing gastric aspirate with corresponding stool sample there was 97% agreement, with Cohen's kappa value of 0.94. There was a statistically significant association observed between gastric aspirate CBNAAT and stool CBNAAT p <0.001 using chi square test. Sensitivity of gastric aspirate CBNAAT and stool CBNAAT was 75% and 73% respectively and specificity was 100% for both the samples compared against Composite Reference Standard (CRS).

CONCLUSIONS

The diagnostic accuracy of stool CBNAAT is comparable to GA CBNAAT in children and can be used as a good alternative to gastric aspirate for diagnosis of pulmonary and disseminated tuberculosis in children.

Stool CBNAAT: Alternative tool in the diagnosis of pulmonary tuberculosis in children

Tuberculosis (TB) remains a significant public health concern, especially in children. The World Health Organization now provides estimates on pediatric TB cases and deaths, underscoring the urgency of addressing this issue. In India, childhood TB contributes significantly to the global burden, with a notable gap between reported cases and estimated incidence. Diagnosing pulmonary TB in children presents challenges, primarily due to difficulties in obtaining suitable respiratory specimens. Rapid tests like Cartridge-Based Nucleic Acid Amplification Test (CBNAAT) have shown promise in enhancing diagnostic sensitivity. Recent research suggests that stool samples offer a non-invasive alternative for diagnosing pulmonary TB in children, with good diagnostic accuracy observed for stool CBNAAT. Furthermore, stool CBNAAT results demonstrate high agreement with gastric aspirate CBNAAT in TB diagnosis. Various stool processing methods, such as centrifugation, filtration, and sedimentation, have shown improved results for CBNAAT testing. However, it is crucial to standardize these methods to ensure consistent and comparable outcomes. Integrating stool CBNAAT into existing diagnostic algorithms for pediatric TB can enhance accuracy and efficiency in diagnosis. When implementing these algorithms, local resources, epidemiological context, and healthcare settings should be taken into account. Stool CBNAAT holds promise for microbiological confirmation of pediatric pulmonary TB, especially in resource-limited settings where obtaining representative respiratory specimens is challenging. Further comparative studies and standardization of stool processing methods are necessary to determine the most suitable approach in different contexts. By doing so, we can make significant strides in improving TB diagnosis and management in children.

Advanced HIV disease: A review of diagnostic and prophylactic strategies

BACKGROUND

Despite expanded access to antiretroviral therapy (ART) and the rollout of the World Health Organization's (WHO) 'test-and-treat' strategy, the proportion of people with HIV (PWH) presenting with advanced HIV disease (AHD) remains unchanged at approximately 30%. Fifty percent of persons with AHD report prior engagement to care. ART failure and insufficient retention in HIV care are major causes of AHD. People living with AHD are at high risk for opportunistic infections and death. In 2017, the WHO published guidelines for the management of AHD that included a comprehensive package of care for screening and prophylaxis of major opportunistic infections (OIs). In the interim, ART regimens have evolved: integrase inhibitors are first-line therapy globally, and the diagnostic landscape is evolving. The objective of this review is to highlight novel point-of-care (POC) diagnostics and treatment strategies that can facilitate OI screening and prophylaxis for persons with AHD.

METHODS

We reviewed the WHO guidelines for recommendations for persons with AHD. We summarized the scientific literature on current and emerging diagnostics, along with emerging treatment strategies for persons with AHD. We also highlight the key research and implementation gaps together with potential solutions.

RESULTS

While POC CD4 testing is being rolled out in order to identify persons with AHD, this alone is insufficient; implementation of the Visitect CD4 platform has been challenging given operational and test interpretation issues. Numerous non-sputum POC TB diagnostics are being evaluated, many with limited sensitivity. Though imperfect, these tests are designed to provide rapid results (within hours) and are relatively affordable for resource-poor settings. While novel POC diagnostics are being developed for cryptococcal infection, histoplasmosis and talaromycosis, implementation science studies are urgently needed to understand the clinical benefit of these tests in the routine care.

CONCLUSIONS

Despite progress with HIV treatment and prevention, a persistent 20%-30% of PWH present to care with AHD. Unfortunately, these persons with AHD continue to carry the burden of HIV-related morbidity and mortality. Investment in the development of additional POC or near-bedside CD4 platforms is urgently needed. Implementation of POC diagnostics theoretically could improve HIV retention in care and thereby reduce mortality by overcoming delays in laboratory testing and providing patients and healthcare workers with timely same-day results. However, in real-world scenarios, people with AHD have multiple comorbidities and imperfect follow-up. Pragmatic clinical trials are needed to understand whether these POC diagnostics can facilitate timely diagnosis and treatment, thereby improving clinical outcomes such as HIV retention in care.

Stool Xpert MTB/RIF as a possible diagnostic alternative to sputum in Africa: a systematic review and meta-analysis

INTRODUCTION

Worldwide, COVID-19 pandemic lead to a large fall in the number of newly reported TB cases. In sub-Saharan Africa, microbiological diagnosis of TB is generally based on smear microscopy and Xpert MTB/RIF on sputum samples, but good quality sputum samples are often difficult to obtain, leading clinicians to rely on more invasive procedures for diagnosis. Aim of this study was to investigate pooled sensitivity and specificity of Xpert MTB/RIF on stool samples compared to respiratory microbiological reference standards in African countries.

METHODS

Four investigators independently searched PubMed, SCOPUS, and Web of Science until 12th October 2022, then screened titles and abstracts of all potentially eligible articles. The authors applied the eligibility criteria, considered the full texts. All the studies reported the data regarding true positive (TP), true negative (TN), false positive (FP) and false negative (FN). Risk of bias and applicability concerns were assessed with the Quadas-2 tool.

RESULTS

overall, among 130 papers initially screened, we evaluated 47 works, finally including 13 papers for a total of 2,352 participants, mainly children. The mean percentage of females was 49.6%, whilst the mean percentage of patients reporting HIV was 27.7%. Pooled sensitivity for Xpert MTB/RIF assay for detecting pulmonary tuberculosis was 68.2% (95%CI: 61.1-74.7%) even if characterized by a high heterogeneity (I2=53.7%). Specificity was almost 100% (99%, 95%CI: 97-100%; I2 = 45.7%). When divided for reference standard, in the six studies using sputum and nasogastric aspirate the accuracy was optimal (AUC = 0.99, SE = 0.02), whilst in the studies using only sputum for tuberculosis detection the AUC was 0.85 (with a SE = 0.16). The most common source of bias was exclusion of enrolled patients in the analysis.

CONCLUSIONS

Our study confirms that, in Africa, stool Xpert MTB/RIF may be a useful rule-in test for children above and below 5 years of age under evaluation for pulmonary tuberculosis. Sensitivity increased substantially when using both sputum and nasogastric aspirate as reference samples.