Stool Xpert® MTB/RIF test for the diagnosis of childhood pulmonary tuberculosis at primary clinics in Zimbabwe

Xpert-Ultra Assay in Stool and Urine Samples to Improve Tuberculosis Diagnosis in Children: The Médecins Sans Frontières Experience in Guinea-Bissau and South Sudan

Background

More than half of childhood tuberculosis cases remain undiagnosed yearly. The World Health Organization recommends the Xpert-Ultra assay as a first pediatric diagnosis test, but microbiological confirmation remains low. We aimed to determine the diagnostic performance of Xpert-Ultra with stool and urine samples in presumptive pediatric tuberculosis cases in 2 high-tuberculosis-burden settings.

Methods

This Médecins Sans Frontières cross-sectional multicentric study took place at Simão Mendes Hospital, Guinea-Bissau (July 2019 to April 2020) and in Malakal Hospital, South Sudan (April 2021 to June 2023). Children aged 6 months to 15 years with presumptive tuberculosis underwent clinical and laboratory assessment, with 1 respiratory and/or extrapulmonary sample (reference standard [RS]), 1 stool, and 1 urine specimen analyzed with Xpert-Ultra.

Results

A total of 563 children were enrolled in the study, 133 from Bissau and 400 from Malakal; 30 were excluded. Confirmation of tuberculosis was achieved in 75 (14.1%), while 248 (46.5%) had unconfirmed tuberculosis. Of 553 with an RS specimen, the overall diagnostic yield was 12.4% (66 of 533). A total of 493 stool and 524 urine samples were used to evaluate the performance of Xpert-Ultra with these samples. Compared with the RS, the sensitivity and specificity of Xpert-Ultra were 62.5% (95% confidence interval, 49.4%-74%) and 98.3% (96.7%-99.2%), respectively, with stool samples, and 13.9% (7.5%-24.3%) and 99.4% (98.1%-99.8%) with urine samples. Nine patients were positive with stool and/or urine samples but negative with the RS.

Conclusions

Xpert-Ultra in stool samples showed moderate to high sensitivity and high specificity compared with the RS and an added diagnostic yield when RS results were negative. Xpert-Ultra in stool samples was useful in extrapulmonary cases. Xpert-Ultra in urine samples showed low test performance.

Clinical Trials Registration

NCT06239337.

Impact of the Stool-Based Xpert Test on Childhood Tuberculosis Diagnosis in Selected States in Nigeria

BACKGROUND

In Nigeria, most children with tuberculosis (TB) present at primary health clinics where there are limited personnel skilled in collecting appropriate respiratory specimens from those who cannot produce sputum. KNCV Nigeria, in collaboration with the National Tuberculosis Control Program, implemented a modified simple, one-step (SOS), stool-based Xpert MTB/RIF method for diagnosis of TB in children who cannot expectorate sputum. We evaluated the impact of its implementation on childhood TB diagnosis.

METHOD

A cross-sectional study was conducted across 14 selected states using secondary data of children presumed to have TB. Stool was collected from children presumed to have TB and processed using Xpert.

RESULT

Out of 52,117 presumptive TB cases, 52% were male and 59.7% were under 5 years old. A total of 2440 (5%) cases were diagnosed with TB, and 2307 (95%) were placed on treatment. Annual TB notifications increased significantly after the introduction of the stool-based Xpert test when compared to those in the pre-implementation period. Increasing contributions from stool testing were observed throughout the implementation period, except in 2020 during the COVID-19 era. Overall, stool Xpert testing improved childhood TB notification in the studied states. Interventions aimed at awareness creation, capacity building, and active case finding improved the performance of the test.

Comparison of gastric lavage/sputum and stool specimens in the diagnosis of pediatric pulmonary tuberculosis- A pilot study

BACKGROUND AND OBJECTIVE

Global TB report 2021 mentions 11 % prevalence of pediatric TB, whereas 5.65% of the cases were reported from India in 2020. India features in the list of TB high burden countries, HIV-TB high burden and MDR-TB high burden countries. The diagnosis of pulmonary tuberculosis in children is difficult as they tend to swallow the sputum, invasive techniques of gastric aspirates needs to be followed and the disease itself is paucibacillary. The disease progresses rapidly in young children and hence rapid diagnosis is needed. Obtaining appropriate respiratory samples for diagnosis is difficult especially in primary care settings. Stool sample is easy to obtain and since children swallow sputum, it can be used to diagnose pulmonary tuberculosis. With this background, a pilot study was planned to evaluate the accuracy of the Xpert MTB/RIF assay for the detection of MTB in stool specimens obtained from pediatric pulmonary TB patients confirmed either by gastric lavage(GL) or sputum(SP) Xpert MTB/RIF assay. In addition, the results of microscopy of stool specimen were compared with that of gastric lavage/ sputum (GL/SP) specimen by Ziehl-Neelsen (ZN) and fluorescent light-emitting diode (LED) staining.

MATERIAL AND METHODS

A prospective study was carried out on 50 GL/SP Xpert MTB/RIF assay positive children (0-14 years). Stool specimens from these children were processed for Xpert MTB/RIF assay. The GL/SP and stool specimens were processed for ZN and Auramine O fluorescent microscopy as well.

RESULTS

Fluorescent staining detected acid fast bacilli (AFB) in 24 GL/SP and 16 stool specimens as compared to 20 GL/SP and 10 stool specimens by ZN staining. Stool Xpert MTB/ RIF assay was positive in 29 out of 50 children. Rifampicin resistance was detected in 13 of the 50 (26%) GL/SP specimens. Of these 13 children, rifampicin resistance was detected in 7 stool specimens, rifampicin indeterminate resistance was detected in one specimen and in the remaining 5 children, M.tuberculosis was not detected in stool.

CONCLUSION

Stool is a good non-invasive specimen for the detection of pulmonary TB in children, especially in remote areas, where invasive techniques cannot be performed for sample collection.

Evaluation of Xpert MTB/RIF Assay on Stool Samples for the Diagnosis of Pulmonary Tuberculosis among the Pediatric Population

Objective  Microbiological confirmation of tuberculosis (TB) in pediatric cases is challenging due to its paucibacillary nature and difficulty in specimen collection. This study aimed to validate stool as an alternative sample for the diagnosis of pediatric pulmonary TB via Xpert MTB/RIF (Xpert) assay. Materials and Methods  This cross-sectional study included 75 pediatric patients up to 10 years of age with signs and symptoms suggestive of TB. From each recruited patient, pulmonary and stool samples were collected in a sterile container. The collected samples were subjected to Ziehl-Neelsen staining, BACTEC MGIT 960 culture (MGIT), Xpert, and in-house multiplex polymerase chain reaction for TB diagnosis. Results  About 13.33% (10/75) of the pulmonary samples and, of them, 50% (5/75) of the stool samples were positive by Xpert assay. The sensitivity and specificity of Xpert assay with stool and pulmonary samples were 50 (95% confidence interval [CI]: 18.71-81.29%) and 100% (95% CI: 94.48-100%), respectively. Conclusion  The Xpert assay on stool samples showed limited sensitivity and good specificity in the diagnosis of pulmonary TB. Therefore, it can be proposed as an alternative screening sample to diagnose TB in pediatric cases for which getting a respiratory sample is extremely difficult. However, further studies with greater number of samples and multiple baseline variables are required to support our findings. Strategies to optimize stool Xpert assay should be performed to enhance the sensitivity of this method to detect Mycobacterium 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.

Use of stool swabs in molecular transport media increases access to Xpert Ultra testing for TB in children

SETTING: Tertiary level hospital in Lusaka, Zambia.OBJECTIVE: To measure concordance between Xpert® MTB/RIF Ultra (Ultra) results of stool with and without transport media, and compare Ultra results from the two stool processing methods to Ultra and culture results using gastric aspirates (GA).DESIGN: This was a cross-sectional study collecting stool and GA from children 0-5 years presenting with signs and symptoms of TB. Stool was processed for Ultra testing by two methods: the Simple-One-Step (SOS) on an aliquot of stool and PrimeStore® MTM Molecular Transport Medium (PS-MTM) using a stool swab.RESULTS: A total of 114 children (median age: 17 months, IQR 7-30) provided both a stool and a GA sample. Stool Ultra results processed using the PS-MTM method showed high concordance with stool Ultra results processed by the SOS method, with only 1/114 discordant results. Concordance with GA Ultra was high as well, as 9/13 Mycobacterium tuberculosis (MTB) cases detected were identified by all three methods.CONCLUSION: Ultra results from stool swabs collected using PS-MTM were equivalent to results from stool using the SOS method and GA. Given that PS-MTM inactivates MTB and stabilises DNA without cold chain, using it for stool has the potential to increase access to a TB diagnosis for children in underserved areas.

Analytical performances of the Xpert MTB/RIF assay using stool specimens to improve the diagnosis of pulmonary tuberculosis in Burkina Faso, a tuberculosis endemic country

Timely diagnosis of Pulmonary Tuberculosis (PTB) is associated with good prognosis, but remains difficult in primary healthcare facilities and particularly in children and patients living with HIV. The aim of this study was to compare the GeneXpert ® MTB/RIF assay (Xpert) performed using a stool sample (3-5 g) and using the first Respiratory Tract Sample (RTS; i.e., sputum, bronchoalveolar or gastric aspirate; as normally done) concomitantly collected from 119 patients with suspected PTB to improve PTB diagnosis in Burkina Faso, a high tuberculosis burden country with limited resources. Overall, microbiological, microscopic and molecular analysis of the 119 first RTS and 119 stool specimens led to Mycobacterium tuberculosis complex detection in 28 patients (23 positive RTS cultures and 5 negative RTS cultures-RTS Xpert positive). When using the 28 clinical confirmed cases as reference standard, the sensitivities of the stool-based and RTS-based Xpert assays were not different (24/28, 85.7%, versus 26/28, 92.86%; p > 0.30), and 22 results were fully concordant. Considering the first RTS culture as the gold standard, the sensitivities of the stool-based and RTS-based Xpert assays to detect PTB in patients with positive RTS culture were 100% (23/23) and 91.3% (21/23), respectively (p >0.05). The stool-based Xpert assay specificity for excluding PTB was 99% (95/96) (compared with 95%, 91/96, when using RTS) and its negative and positive predictive values were 100% (95/95) and 96% (23/24), respectively. Compared with the 23 positive RTS cultures, the incremental yield rates of the RTS-based and stool-based Xpert assays were 4.2% (5/119) and 0.84% (1/119), respectively. Overall, our findings support using the stool-based Xpert assay as an alternative method for earlier PTB diagnosis, when RTS are difficult to obtain.

Comparison of Xpert MTB/RIF Ultra Results of Stool and Sputum in Children with Presumptive Tuberculosis in Southern Ethiopia

The introduction of stool as a readily obtainable sample and the recently developed simple one-step (SOS) stool processing method on Xpert MTB/RIF Ultra (Xpert Ultra) offer an opportunity for TB diagnosis in children. We conducted this study in secondary health facilities in Ethiopia, which are the first-level referral facilities for childhood TB diagnosis and treatment, with the aim to determine if stool-based TB diagnosis can be performed with a reasonable level of concordance with sputum tests using Xpert MTB/RIF Ultra. Eligible children 0-14 years old with presumptive pulmonary TB were asked to provide stools in addition to routinely requested sputum samples. We determined the level of agreement between the stool and sputum test results. Of the 373 children included in the study, 61% were <5 years of age and 56% were male. Thirty-six children (9.7%) were diagnosed with TB, and all started treatment. The rate of concordance between stool and sputum was high, with a kappa value of 0.83 (p < 0.001). There were more Xpert Ultra positive results on stool (n = 27 (7.2%)) than on sputum/NGA (n = 23 (6.2%)). Laboratories in secondary hospitals can perform stool-based TB diagnosis in children, with high concordance between stool and sputum test results reaffirming the applicability of the SOS stool method.

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.

Diagnostic accuracy of Xpert MTB/RIF Ultra and culture assays to detect Mycobacterium Tuberculosis using OMNIgene-sputum processed stool among adult TB presumptive patients in Uganda

BACKGROUND

Stool is a potential sample for diagnosing Mycobacterium tuberculosis (Mtb) in patients with difficulty in expectorating. However, high mycobacterial culture contamination rates and Xpert MTB/RIF Ultra test error rates on stool samples have limited its use. OMNIgene SPUTUM (OM-S) is a sample transport reagent with characteristics of sputum decontamination while maintaining viable Mtb. We evaluated the impact of OM-S on Mtb diagnostic yield from stool using smear microscopy, Xpert MTB/RIF Ultra, and culture among presumptive TB patients.

METHODS

Paired stool and expectorated sputum samples were collected from consecutive Ugandan adults undergoing diagnostic evaluation for pulmonary TB between June 2018 and June 2019. Stool was divided into 2 portions: one was homogenized in OM-S (OM-S stool) and the other in PBS (PBS stool) as control. Both sputum and processed stool were tested for Mtb using concentrated smear fluorescence microscopy (CFM), Xpert MTB/RIF Ultra (Xpert) and Mycobacteria Growth Indicator Tube (MGIT) culture. Sensitivity, specificity, and predictive values for each test were calculated against sputum MGIT culture as the reference standard.

RESULTS

Of the 200 participants, 120 (60%) were male, 73 (37%) were HIV positive (median CD4 120 cells/uL (IQR 43-297)) and 128 (64%) had confirmed pulmonary TB by sputum MGIT culture. Seven (4%) OM-S stool Xpert samples reported errors while 47 (25%) and 103 (61%) were contaminated on OM-S stool MGIT and PBS stool MGIT, respectively. OM-S stool MGIT was able to accurately diagnose 56 of the contaminated PBS stool MGIT samples compared to only 5 of the contaminated OM-S stool MGIT samples diagnosed by PBS stool MGIT. Sensitivity (95% Confidence Interval, CI) 89% (83-94) for OM-S stool Xpert was higher compared to that of OM-S stool MGIT 60% (51-69) and PBS stool MGIT 42% (32-52). Specificity (95%CI) 91% (82-97) was also higher for OM-S stool Xpert compared to OM-S stool MGIT 64% (51-75) and PBS stool MGIT 26% (16-38).

CONCLUSION

Stool processed with OM-S showed potential to improve Mtb diagnostic yield and reduce rates of indeterminate results when tested on Xpert and MGIT culture. The method may thus be of value in Mtb detection among patients with difficulty to expectorate.

Development of a Clinical Prediction Score Including Monocyte-to-Lymphocyte Ratio to Inform Tuberculosis Treatment Among Children With HIV: A Multicountry Study

Background

Clinical pediatric tuberculosis (TB) diagnosis may lead to overdiagnosis particularly among children with human immunodeficiency virus (CHIV). We assessed the performance of monocyte-lymphocyte ratio (MLR) as a diagnostic biomarker and constructed a clinical prediction score to improve specificity of TB diagnosis in CHIV with limited access to microbiologic testing.

Methods

We pooled data from cohorts of children aged ≤13 years from Vietnam, Cameroon, and South Africa to validate the use of MLR ≥0.378, previously found as a TB diagnostic marker among CHIV. Using multivariable logistic regression, we created an internally validated prediction score for diagnosis of TB disease in CHIV.

Results

The combined cohort had 601 children (median age, 1.9 [interquartile range, 0.9-5.3] years); 300 (50%) children were male, and 283 (47%) had HIV. Elevated MLR ≥0.378 had sensitivity of 36% (95% confidence interval [CI], 23%-51%) and specificity of 79% (95% CI, 71%-86%) among CHIV in the validation cohort. A model using MLR ≥0.28, age ≥4 years, tuberculin skin testing ≥5 mm, TB contact history, fever >2 weeks, and chest radiograph suggestive of TB predicted active TB disease in CHIV with an area under the receiver operating characteristic curve of 0.85. A prediction score of ≥5 points had a sensitivity of 94% and specificity of 48% to identify confirmed TB, and a sensitivity of 82% and specificity of 48% to identify confirmed and unconfirmed TB groups combined.

Conclusions

Our score has comparable sensitivity and specificity to algorithms including microbiological testing and should enable clinicians to rapidly initiate TB treatment among CHIV when microbiological testing is unavailable.

Pediatric Tuberculosis Management: A Global Challenge or Breakthrough?

Managing pediatric tuberculosis (TB) remains a public health problem requiring urgent and long-lasting solutions as TB is one of the top ten causes of ill health and death in children as well as adolescents universally. Minors are particularly susceptible to this severe illness that can be fatal post-infection or even serve as reservoirs for future disease outbreaks. However, pediatric TB is the least prioritized in most health programs and optimal infection/disease control has been quite neglected for this specialized patient category, as most scientific and clinical research efforts focus on developing novel management strategies for adults. Moreover, the ongoing coronavirus pandemic has meaningfully hindered the gains and progress achieved with TB prophylaxis, therapy, diagnosis, and global eradication goals for all affected persons of varying age bands. Thus, the opening of novel research activities and opportunities that can provide more insight and create new knowledge specifically geared towards managing TB disease in this specialized group will significantly improve their well-being and longevity.

Stool-based Xpert MTB/RIF assay for the diagnosis of pulmonary tuberculosis in children at a teaching and referral hospital in Southwest Ethiopia

BACKGROUND

Diagnosis of tuberculosis (TB) in children is challenging mainly due to the difficulty of obtaining respiratory specimen and lack of sensitive diagnostic tests. The objective of this study was to evaluate the diagnostic performance of Xpert MTB/RIF (Xpert here after) for the diagnosis of pulmonary TB (PTB) from stool specimen in children.

METHODS

A cross-sectional study was conducted among consecutively recruited children (less than 15 years old) with presumptive PTB at Jimma Medical Center, Ethiopia. One pulmonary specimen (expectorated sputum or gastric aspirate) was collected from each participant and tested for TB by Xpert and Lowenstein-Jensen (LJ) culture. In addition, one stool specimen per child was collected and tested by Xpert after a single step, centrifuge-free stool processing method adapted from KNCV TB Foundation. Diagnostic performance of Xpert was calculated with reference to LJ culture and to a composite reference standards (CRS) comprising of confirmed TB (positive by Xpert and/or culture) and unconfirmed TB (clinical diagnosis with improvement after anti-TB treatment).

RESULTS

A total of 178 children were enrolled; 152 of whom had complete microbiological results. Overall, TB was diagnosed in 13.2% (20/152) of the children with presumptive TB. Of these, only ten had microbiologically confirmed TB (positive Xpert and/or culture) and the remaining ten were clinically diagnosed with positive response to anti-TB treatment and were classified as unconfirmed TB. Stool Xpert had sensitivity of 100% (95%CI: 66.4-100) and specificity of 99.3% (95%CI: 96.2-100) compared to culture; however, the sensitivity was decreased to 50% (95%CI: 27.2-72.8) when compared to CRS. The Xpert on gastric aspirate had sensitivity of 77.8% (95%CI: 40-97.2) compared to culture and 40% (95%CI: 19.1-64) compared to CRS.

CONCLUSIONS

The sensitivity of Xpert for stool sample is comparable to that for gastric aspirate. Stool sample is a potential alternative to pulmonary specimen in the diagnosis of pulmonary TB in children using Xpert.

Utility of stool CBNAAT in the diagnosis of pediatric pulmonary tuberculosis in India

BACKGROUND

India houses 27% of the tuberculosis cases worldwide. Pediatric tuberculosis accounts for 11% cases worldwide. Microbiological confirmation of diagnosis is difficult in children. We aimed to study the proportion of Stool CBNAAT (Cartridge Based Nucleic Acid Amplification Test) and GA CBNAAT positive cases among the presumptive cases of tuberculosis in children and assess diagnostic utility of the Stool CBNAAT in comparison to GA CBNAAT and culture.

METHODS

Ours was a cross sectional study. 75 children, aged 6 months to 12 years who were presumptive cases of pulmonary tuberculosis and who were unable to expectorate, were enrolled. Gastric aspirate and stool samples were obtained and CBNAAT and culture was done. Results of stool CBNAAT were compared with GA CBNAAT and culture.

RESULTS

Of the 75 children enrolled, 28 were started on antitubercular therapy, 12 of whom were microbiologically confirmed and 16 were started on clinical grounds. Overall, 10 (13.3%) and 11 (14.6%) were positive by Stool CBNAAT and GA CBNAAT respectively. GA CBNAAT and Stool CBNAAT were found to have near perfect agreement (Cohen's kappa 0.834). Stool CBNAAT had sensitivity and specificity of 73% and 97% as compared to culture.

CONCLUSIONS

Stool CBNAAT may be used for bacteriological confirmation of pediatric pulmonary tuberculosis. It was found to have a high degree of concordance with the conventionally used GA CBNAAT. This test would be helpful in endemic countries where there is a dearth of trained staff, especially in the periphery, to obtain gastric aspirate. Discomfort associated with sampling would be avoided.

High Mycobacterium tuberculosis Bacillary Loads Detected by Tuberculosis Molecular Bacterial Load Assay in Patient Stool: a Potential Alternative for Nonsputum Diagnosis and Treatment Response Monitoring of Tuberculosis

Not all patients produce sputum, yet most available TB tests use sputum. We investigated the utility of a novel RNA-based quantitative test, the tuberculosis molecular bacterial load assay (TB-MBLA), for the detection and quantification of Mycobacterium tuberculosis in stool. Stools from 100 adult individuals were treated with OMNIgene-sputum reagent and tested using Xpert MTB/RIF ultra (Xpert ultra), auramine O smear microscopy (smear), mycobacterial growth indicator tube (MGIT), and Lowenstein-Jensen (LJ) cultures. The remaining portions were frozen at −20°C and later tested by TB-MBLA. MGIT sputum culture was used as a TB confirmatory test and reference for stool tests. Sixty-one of 100 participants were already confirmed TB positive by MGIT sputum culture, 20 (33%) of whom were HIV coinfected. TB-MBLA detected M. tuberculosis in 57/100 stool samples, including 49 already confirmed for TB. The mean bacterial load measured by stool TB-MBLA was 5.67 ± 1.7 log₁₀ estimated CFU (eCFU) per mL in HIV-coinfected participants, which was higher than the 4.83 ± 1.59 log₁₀ eCFU per mL among the HIV-negative participants (P = 0.04). The sensitivities (95% confidence intervals [CI]) of stool assays were 80% (68 to 89) and 90% (79 to 98) for TB-MBLA and Xpert ultra, which were both higher than the 44% (32 to 58), 64% (51 to 76), and 62% (45 to 77) for smear, MGIT, and Lowenstein-Jensen (LJ) stool cultures, respectively. The specificity (95% CI) of stool assays was highest for smear, at 97% (87 to 100), followed by Xpert ultra at 91% (76 to 98), TB-MBLA at 79% (63 to 90), LJ at 80% (64 to 91), and MGIT at 62% (45 to 77). Twenty-six percent of MGIT and 21% of LJ stool cultures were indeterminate due to contamination. Detection and quantification of viable M. tuberculosis bacilli in stool raises its utility as an alternative to sputum as a sample type for TB diagnosis.

IMPORTANCE This paper highlights the value of stool as a sample type for diagnosis of tuberculosis. While other studies have used DNA-based assays like the Xpert MTB/RIF and culture to detect Mycobacterium tuberculosis in stool, this is the first study that has applied TB-MBLA, an RNA-based assay, to quantify TB bacteria in stool. The high microbial density and diversity in stool compromises the specificity and sensitivity of culture-based tests due to overgrowth of non-M. tuberculosis flora. Consequently, TB-MBLA becomes the most sensitive and specific test for the detection and quantification of viable TB bacteria in stool. Most crucially, this study raises the possibility of a nonsputum alternative sample type for diagnosis of TB among people who have difficulty in producing sputum.

Paediatric tuberculosis diagnosis using Mycobacterium tuberculosis real-time polymerase chain reaction assay: a systematic review and meta-analysis

BACKGROUND

Rapid and accurate diagnosis of paediatric tuberculosis (TB) is key to manage the disease and to control and prevent its transmission. Collection of quality sputum samples without invasion methods from paediatrics (age < 16 years) with presumptive pulmonary tuberculosis (PTB) remains a challenge. Thus, the aim of this meta-analysis was to assess the overall accuracy of a real-time polymerase chain reaction (RT-PCR)-based assay, for routine diagnosis of MTB in different samples from paediatrics with active pulmonary and extra-pulmonary tuberculosis using mycobacterial culture as the gold standard in clinical microbiology laboratories.

METHODS

We conducted a systematic review and meta-analysis to examine the diagnostic test accuracy of RT-PCR based assay for the detection of MTB in paediatric clinical samples. A systematic literature search was performed for publications in any language. MEDLINE via PubMed, EMBASE, and Web of Science were among 9 bibliographic databases searched from August 2019 until November 2020. Bivariate random-effects model of meta-analysis were performed to generate pooled summary estimates (95% CIs) for overall accuracy of RT-PCR based assay compared to mycobacterial culture as the reference standard.

RESULTS

Of the 1592 candidate studies, twenty-one eligible studies met our inclusion criteria. In total, the review and meta-analysis included 5536 (3209 PTB and 2327 EPTB). Summary estimates for pulmonary TB (11 studies) were as follows: sensitivity 56 (95% CI 51-62), specificity 97 (95% CI 96-98) and summary estimates for extra-pulmonary TB (10 studies) were as follows: sensitivity 87 (95% CI 82-91)) specificity 100 (95% CI 99-100). There was significant heterogeneity in sensitivity and specificity among the enrolled studies (p < 0.001).

CONCLUSIONS

Our results suggested that the RT-PCR based assay could be a useful test for the diagnosis of paediatrics TB with high sensitivity and specificity in low-income/high-burden and upper medium income/low-burden settings. From the study, RT-PCR assay demonstrated a high degree of sensitivity for extra-pulmonary TB and good sensitivity for pulmonary TB which is an important factor in achieving effective global control and for patient management in terms of initiating early and appropriate anti-tubercular therapy.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018104052.

Xpert Ultra Assay on Stool to Diagnose Pulmonary Tuberculosis in Children

Background

The World Health Organization recommends the Xpert MTB/RIF Ultra assay for diagnosing pulmonary tuberculosis (PTB) in children. Though stool is a potential alternative to respiratory specimens among children, the diagnostic performance of Xpert Ultra on stool is unknown. Thus, we assessed the diagnostic performance of Xpert Ultra on stool to diagnose PTB in children.

Methods

We conducted a cross-sectional study among consecutively recruited children (< 15 years of age) with presumptive PTB admitted in 4 tertiary care hospitals in Dhaka, Bangladesh, between January 2018 and April 2019. Single induced sputum and stool specimens were subjected to culture, Xpert, and Xpert Ultra. We considered children as bacteriologically confirmed on induced sputum if any test performed on induced sputum was positive for Mycobacterium tuberculosis and bacteriologically confirmed if M. tuberculosis was detected on either induced sputum or stool.

Results

Of 447 children, 29 (6.5%) were bacteriologically confirmed on induced sputum and 72 (16.1%) were bacteriologically confirmed. With “bacteriologically confirmed on induced sputum” as a reference, the sensitivity and specificity of Xpert Ultra on stool were 58.6% and 88.1%, respectively. Xpert on stool had sensitivity and specificity of 37.9% and 100.0%, respectively. Among bacteriologically confirmed children, Xpert Ultra on stool was positive in 60 (83.3%), of whom 48 (80.0%) had “trace call.”

Conclusions

In children, Xpert Ultra on stool has better sensitivity but lesser specificity than Xpert. A high proportion of Xpert Ultra assays positive on stool had trace call. Future longitudinal studies on clinical evolution are required to provide insight on the management of children with trace call.

Variable Diagnostic Performance of Stool Xpert in Pediatric Tuberculosis: A Systematic Review and Meta-analysis

BACKGROUND

Difficult specimen collection and low bacillary load make microbiological confirmation of tuberculosis (TB) in children challenging. In this study, we conducted a systematic review and meta-analysis to assess the diagnostic accuracy of Xpert on stool for pediatric tuberculosis.

METHODS

Our search included studies from 2011 through 2019, and specific search terms were used to retrieve articles from Pubmed, EMBASE, BIOSIS, ClinicalTrials.gov, and Google Scholar. Risk of bias was assessed using the QUADAS 2 tool. The protocol was registered in PROSPERO (CRD42018083637). Summary estimates of sensitivity and specificity were conducted using meta-disc Software assuming a random-effects model.

RESULTS

We identified 12 eligible studies, which included data from 2177 children, of whom 295 (13.6%) had bacteriologically confirmed TB on respiratory specimens. The pooled sensitivity of Xpert MTB/RIF on stool specimens compared with bacteriologically confirmed tuberculosis with respiratory specimens was 0.50 (95% CI, 0.44-0.56) with an I 2 of 86%, which was statistically significant (P < .001). The pooled specificity was 0.99 (95% CI, 0.98-0.99; I 2 = 0.0%; P = .44).

CONCLUSIONS

Despite the observed heterogeneity, stool may be considered an additional specimen to support diagnosis of pulmonary TB in children, especially in settings where it is impossible to get respiratory samples. Further studies should evaluate its optimization as a diagnostic tool.

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

SETTING

Six health facilities in Dar es Salaam, Tanzania.

OBJECTIVE

To evaluate the use of stool specimens in the diagnostic workup of paediatric TB using the Xpert^® MTB/RIF assay.

DESIGN

Between December 2018 and May 2019, we performed a cross-sectional diagnostic study of children aged between 1 month and 14 years with presumptive TB. A single stool specimen was tested using Xpert. The result was compared with the reference microbiological standard for respiratory or gastric specimens tested using Xpert and/or solid culture. The sensitivity, specificity and predictive values of stool Xpert assay were assessed.

RESULTS

A total of 225 children with a median age of 2.17 years (IQR 1.16-5.19) were enrolled; 165/225 (73.3%) were aged <5 years. Of 225 children, 8 (3.6%) were diagnosed with TB as they were culture- or Xpert-positive on sputum/gastric aspirate. The stool Xpert assay showed a sensitivity of 62.5% (95% CI 25-92) and specificity of 100% (95% CI 98-100) against the reference standard.

CONCLUSION

Use of the Xpert assay on stool specimens had a moderate sensitivity and high specificity in the diagnosis of pulmonary TB in children. Our data adds to the body of evidence for the use of Xpert assay on stool as a non-respiratory specimen to complement conventional methods used to diagnose the disease.

Tuberculosis diagnostic accuracy of stool Xpert MTB/RIF and urine AlereLAM in vulnerable children

BACKGROUND

Non-sputum based diagnostic approaches are crucial in children at high risk of disseminated tuberculosis [TB] who cannot expectorate sputum. We evaluated the diagnostic accuracy of Xpert MTB/RIF from stool and urine AlereLipoarabinomannan [LAM] test in this group of children.

METHODS

Hospitalised children with presumptive TB and either age <2 years, HIV-positive or severe malnutrition were enrolled in a diagnostic cohort. At enrolment, we attempted to collect two urine, two stool and two respiratory samples. Urine and stool were tested with AlereLAM and Xpert MTB/RIF, respectively. Respiratory samples were tested with Xpert MTB/RIF and mycobacterial culture. Both a microbiological and a composite clinical reference standard were used.

RESULTS

The study enrolled 219 children; median age 16.4 months, 72 (32.9%) HIV-positive and 184 (84.4%) severely malnourished. Twelve (5.5%) and 58 (28.5%) children had confirmed and unconfirmed TB respectively. Stool and urine were collected in 219 (100%) and 216 (98.6%) children. Against the microbiological reference standard the sensitivity and specificity (n/N, 95% confidence intervals) of stool Xpert MTB/RIF was 50.0% (6/12, 21.1-78.9) and 99.1% (198/200 96.4-99.9), while that of urine AlereLAM was 50.0% (6/12, 21.1-78.9) and 74.6% (147/197, 67.9-80.5) respectively. Against the composite reference standard sensitivity was reduced to 11.4% (8/70) for stool and 26.2% (17/68) for urine, with no major difference by age group (<2 and >2 years) or HIV status.

CONCLUSION

The Xpert MTB/RIF assay has excellent specificity on stool, but sensitivity is suboptimal. Urine AlereLAM is compromised by poor sensitivity and specificity in children.

Stool-based Xpert MTB/RIF Ultra assay as a tool for detecting pulmonary tuberculosis in children with abnormal chest imaging: A prospective cohort study

OBJECTIVES

To evaluate the diagnostic efficacy of stool-based Xpert MTB/RIF Ultra assay versus other assays for the detection of paediatric pulmonary tuberculosis (PTB).

METHODS

A prospective head-to-head comparative study was conducted from Dec 2017 to May 2019 in Shanghai Public Health Clinical Centre. Samples were collected from children (< 15 years) with abnormal chest imaging (X-ray or CT scan) results for the following tests: Ultra on stool sample (Ultra-Stool), Ultra on respiratory tract sample (Ultra-RTS), Xpert MTB/RIF assay (Xpert) on RTS (Xpert-RTS), acid-fast bacilli smear on RTS (AFB-RTS), and Mycobacterium tuberculosis (Mtb) culture on RTS (Culture-RTS). The results were compared with a composite reference standard.

RESULTS

A total of 126 cases with paired results were analysed. Against a composite reference standard, Ultra-RTS demonstrated the highest sensitivity (52%) and specificity (100%). Ultra-Stool showed 84.1% concordance with Ultra-RTS, demonstrating 45.5% sensitivity and 94.7% specificity (kappa = 0.65, 95% CI= 0.51-0.79). The sensitivity of Ultra-Stool was similar to Mtb culture (45.5%, p = 1.000) and higher than AFB-RTS (27.3%, p < 0.05). Assay positivity was associated with age and infiltration range in chest imaging.

CONCLUSIONS

When RTS is difficult to obtain, stool sample-based Ultra is a comparable alternative.

Laboratory development of a simple stool sample processing method diagnosis of pediatric tuberculosis using Xpert Ultra

Stool samples are alternatives to respiratory samples for bacteriological confirmation of childhood tuberculosis but require intensive laboratory processing before molecular testing to remove PCR inhibitors and debris. We aimed to develop a centrifuge-free processing method for use in resource-limited settings based on a sucrose-flotation method that showed good sensitivity for childhood tuberculosis diagnosis. In an in vitro study using Xpert MTB/RIF Ultra on stool samples spiked with defined bacterial concentrations of Mycobacterium tuberculosis (MTB), we compared different simplification parameters to the reference sucrose-flotation method. Best methods were selected based on the rate of invalid/error results and on sensitivity, compared to the reference method on stools spiked at 10³ colony forming units (CFU)/g MTB. For final selection, we tested the best parameter combinations at 10² CFU/g. Out of 13 different parameter combinations, three were tested at 10² CFU/g. The best combination used 0.5 g stool, manual shaking, no filtration, 30-min sedimentation, and a 1:3.6 dilution ratio. This method gave 10% invalid/error results and a sensitivity of 70% vs 63% at 10³ CFU/g and 53% vs 58% at 10² CFU/g compared to the reference method. This pre-clinical study was able to develop a centrifuge-free processing method to facilitate stool Xpert Ultra testing.

Xpert MTB/RIF and Xpert MTB/RIF Ultra assays for active tuberculosis and rifampicin resistance in children

BACKGROUND

Every year, at least one million children become ill with tuberculosis and around 200,000 children die. Xpert MTB/RIF and Xpert Ultra are World Health Organization (WHO)-recommended rapid molecular tests that simultaneously detect tuberculosis and rifampicin resistance in adults and children with signs and symptoms of tuberculosis, at lower health system levels. To inform updated WHO guidelines on molecular assays, we performed a systematic review on the diagnostic accuracy of these tests in children presumed to have active tuberculosis.

OBJECTIVES

Primary objectives • To determine the diagnostic accuracy of Xpert MTB/RIF and Xpert Ultra for (a) pulmonary tuberculosis in children presumed to have tuberculosis; (b) tuberculous meningitis in children presumed to have tuberculosis; (c) lymph node tuberculosis in children presumed to have tuberculosis; and (d) rifampicin resistance in children presumed to have tuberculosis - For tuberculosis detection, index tests were used as the initial test, replacing standard practice (i.e. smear microscopy or culture) - For detection of rifampicin resistance, index tests replaced culture-based drug susceptibility testing as the initial test Secondary objectives • To compare the accuracy of Xpert MTB/RIF and Xpert Ultra for each of the four target conditions • To investigate potential sources of heterogeneity in accuracy estimates - For tuberculosis detection, we considered age, disease severity, smear-test status, HIV status, clinical setting, specimen type, high tuberculosis burden, and high tuberculosis/HIV burden - For detection of rifampicin resistance, we considered multi-drug-resistant tuberculosis burden • To compare multiple Xpert MTB/RIF or Xpert Ultra results (repeated testing) with the initial Xpert MTB/RIF or Xpert Ultra result SEARCH METHODS: We searched the Cochrane Infectious Diseases Group Specialized Register, MEDLINE, Embase, Science Citation Index, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, the WHO International Clinical Trials Registry Platform, ClinicalTrials.gov, and the International Standard Randomized Controlled Trials Number (ISRCTN) Registry up to 29 April 2019, without language restrictions.

SELECTION CRITERIA

Randomized trials, cross-sectional trials, and cohort studies evaluating Xpert MTB/RIF or Xpert Ultra in HIV-positive and HIV-negative children younger than 15 years. Reference standards comprised culture or a composite reference standard for tuberculosis and drug susceptibility testing or MTBDRplus (molecular assay for detection of Mycobacterium tuberculosis and drug resistance) for rifampicin resistance. We included studies evaluating sputum, gastric aspirate, stool, nasopharyngeal or bronchial lavage specimens (pulmonary tuberculosis), cerebrospinal fluid (tuberculous meningitis), fine needle aspirates, or surgical biopsy tissue (lymph node tuberculosis).

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed study quality using the Quality Assessment of Studies of Diagnostic Accuracy - Revised (QUADAS-2). For each target condition, we used the bivariate model to estimate pooled sensitivity and specificity with 95% confidence intervals (CIs). We stratified all analyses by type of reference standard. We assessed certainty of evidence using the GRADE approach.

MAIN RESULTS

For pulmonary tuberculosis, 299 data sets (68,544 participants) were available for analysis; for tuberculous meningitis, 10 data sets (423 participants) were available; for lymph node tuberculosis, 10 data sets (318 participants) were available; and for rifampicin resistance, 14 data sets (326 participants) were available. Thirty-nine studies (80%) took place in countries with high tuberculosis burden. Risk of bias was low except for the reference standard domain, for which risk of bias was unclear because many studies collected only one specimen for culture. Detection of pulmonary tuberculosis For sputum specimens, Xpert MTB/RIF pooled sensitivity (95% CI) and specificity (95% CI) verified by culture were 64.6% (55.3% to 72.9%) (23 studies, 493 participants; moderate-certainty evidence) and 99.0% (98.1% to 99.5%) (23 studies, 6119 participants; moderate-certainty evidence). For other specimen types (nasopharyngeal aspirate, 4 studies; gastric aspirate, 14 studies; stool, 11 studies), Xpert MTB/RIF pooled sensitivity ranged between 45.7% and 73.0%, and pooled specificity ranged between 98.1% and 99.6%. For sputum specimens, Xpert Ultra pooled sensitivity (95% CI) and specificity (95% CI) verified by culture were 72.8% (64.7% to 79.6%) (3 studies, 136 participants; low-certainty evidence) and 97.5% (95.8% to 98.5%) (3 studies, 551 participants; high-certainty evidence). For nasopharyngeal specimens, Xpert Ultra sensitivity (95% CI) and specificity (95% CI) were 45.7% (28.9% to 63.3%) and 97.5% (93.7% to 99.3%) (1 study, 195 participants). For all specimen types, Xpert MTB/RIF and Xpert Ultra sensitivity were lower against a composite reference standard than against culture. Detection of tuberculous meningitis For cerebrospinal fluid, Xpert MTB/RIF pooled sensitivity and specificity, verified by culture, were 54.0% (95% CI 27.8% to 78.2%) (6 studies, 28 participants; very low-certainty evidence) and 93.8% (95% CI 84.5% to 97.6%) (6 studies, 213 participants; low-certainty evidence). Detection of lymph node tuberculosis For lymph node aspirates or biopsies, Xpert MTB/RIF pooled sensitivity and specificity, verified by culture, were 90.4% (95% CI 55.7% to 98.6%) (6 studies, 68 participants; very low-certainty evidence) and 89.8% (95% CI 71.5% to 96.8%) (6 studies, 142 participants; low-certainty evidence). Detection of rifampicin resistance Xpert MTB/RIF pooled sensitivity and specificity were 90.0% (67.6% to 97.5%) (6 studies, 20 participants; low-certainty evidence) and 98.3% (87.7% to 99.8%) (6 studies, 203 participants; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

We found Xpert MTB/RIF sensitivity to vary by specimen type, with gastric aspirate specimens having the highest sensitivity followed by sputum and stool, and nasopharyngeal specimens the lowest; specificity in all specimens was > 98%. Compared with Xpert MTB/RIF, Xpert Ultra sensitivity in sputum was higher and specificity slightly lower. Xpert MTB/RIF was accurate for detection of rifampicin resistance. Xpert MTB/RIF was sensitive for diagnosing lymph node tuberculosis. For children with presumed tuberculous meningitis, treatment decisions should be based on the entirety of clinical information and treatment should not be withheld based solely on an Xpert MTB/RIF result. The small numbers of studies and participants, particularly for Xpert Ultra, limits our confidence in the precision of these estimates.

Monocyte-to-Lymphocyte Ratio Is Associated With Tuberculosis Disease and Declines With Anti-TB Treatment in HIV-Infected Children

BACKGROUND

The blood monocyte-to-lymphocyte ratio (MLR) is associated with active tuberculosis (TB) in adults but has not been evaluated as a TB diagnostic biomarker in HIV-infected children in whom respiratory sampling is difficult.

SETTING

In a cohort of HIV-infected hospitalized Kenyan children initiating antiretroviral therapy, absolute monocyte and lymphocyte counts were determined at enrollment and 4, 12, and 24 weeks thereafter.

METHODS

Children were classified as confirmed, unconfirmed, or unlikely pulmonary TB. Receiver operating characteristic curves of MLR cutoff values were generated to distinguish children with confirmed TB from those with unconfirmed and unlikely TB. General estimating equations were used to estimate change in the MLR over time by TB status.

RESULTS

Of 160 children with median age 23 months, 13 (8.1%) had confirmed TB and 67 (41.9%) had unconfirmed TB. The median MLR among children with confirmed TB {0.407 [interquartile range (IQR) 0.378-0.675]} was higher than the MLR in children with unconfirmed [0.207 (IQR 0.148-0.348), P < 0.01] or unlikely [0.212 (IQR 0.138-0.391), P = 0.01] TB. The MLR above 0.378 identified children with confirmed TB with 77% sensitivity, 78% specificity, 24% positive predictive value, and 97% negative predictive value. After TB treatment, the median MLR declined in children with confirmed TB and levels were similar to children with unlikely TB after 12 weeks.

CONCLUSIONS

The blood MLR distinguished HIV-infected children with confirmed TB from those with unlikely TB and declined with TB treatment. The MLR may be a useful diagnostic tool for TB in settings where respiratory-based microbiologic confirmation is inaccessible.

Diagnostic accuracy of molecular detection of Mycobacterium tuberculosis in pediatric stool samples: A systematic review and meta-analysis

BACKGROUND

Stool is a promising specimen option to diagnose pediatric tuberculosis (TB), but studies have reported a wide range of test sensitivities. We conducted a meta-analysis to assess the accuracy of Xpert MTB/RIF or 'in-house' molecular tests on stool samples against culture or Xpert MTB/RIF on respiratory samples or clinically-diagnosed unconfirmed TB and aimed to identify factors that contribute to the heterogeneity of reported sensitivity.

METHODS

We searched EMBASE and Pubmed databases and conference abstract books for studies reporting molecular stool testing against a clinical or microbiological reference standard among children.

RESULTS

We identified 16 studies that included 2,481 children in stool test analyses. Pooled specificity was 98% [95%CI: 96-99], pooled sensitivity was 57% [95%CI: 40-72] against culture and 3% [95%CI: 2-6] among children with clinically-diagnosed, unconfirmed TB. There was much heterogeneity. Sensitivity was higher among children with a smear-positive sputum test. Rifampin resistance in stool was reported in two studies and detected in 5/14 children (36%).

CONCLUSION

Our results suggest molecular stool tests have potential as diagnostic rule-in tests, but it is challenging to optimize sensitivity due to between-study variation in methodology and test procedures. Therefore, we recommend future research with rigorous study design and standardized results reporting.

HIV-associated pediatric tuberculosis: prevention, diagnosis and treatment

PURPOSE OF REVIEW

The detrimental synergy of colliding HIV and tuberculosis (TB) epidemics is most devastating among children and adolescents living with HIV (CALWH) who shoulder a disproportionate burden of all child TB mortality.

RECENT FINDINGS

CALWH benefit less from Bacille-Calmette Guerin vaccination than HIV-uninfected children and are not receiving TB preventive therapy despite global recommendations. Further, the predictive utility of most diagnostic tools is reduced in CALWH. Finally, antiretroviral and anti-TB drug interactions continue to complicate cotreatment for children. Despite these challenges, recent data fuel a new awareness of TB as a hidden cause of child mortality and a renewed commitment to TB prevention. New diagnostic approaches using existing tools with novel specimens, such as stool, may improve the diagnosis of TB in CALWH. Further, pharmacokinetic studies and the development of new drug formulations promise better treatment options for CALWH in the near future.

SUMMARY

With the awareness that TB is the leading cause of mortality among CALWH, comes a responsibility to accelerate research to prevent, diagnose and treat TB in this vulnerable population. In the present, we must adopt evidence-based preventive and treatment strategies to enhance outcomes of CALWH and combating TB.

Detection of Mycobacterium tuberculosis in pediatric stool samples using TruTip technology

Background

Rapid and accurate diagnosis of childhood tuberculosis (TB) is challenging because children are often unable to produce the sputum sample required for conventional tests. Stool is an alternative sample type that is easy to collect from children, and studies investigating the use of stool for molecular detection of Mycobacterium tuberculosis (Mtb) have led to promising results. Our objective was to evaluate stool as an alternative specimen to sputum for Mtb detection in children. We did so using the TruTip workstation (Akonni Biosystems), a novel automated lysis and extraction platform.

Methods

We tested stool samples from 259 children aged 0–14 years old, in Lima, Peru who presented with TB symptoms. Following extraction with TruTip, we detected the presence of Mtb DNA by IS6110 real-time PCR. We calculated assay sensitivity in two groups: (1) children with culture confirmed TB (N = 22); and (2) children with clinically-diagnosed unconfirmed TB (N = 84). We calculated specificity among children in whom TB was ruled out (N = 153). Among children who were diagnosed with TB, we examined factors associated with a positive stool test.

Results

Assay sensitivity was 59% (95% confidence interval [CI]: 39–80%) and 1.2% (95% CI: 0.0–6.5%) in children with culture-confirmed and clinically-diagnosed unconfirmed TB, respectively, and specificity was 97% (95% CI: 93–99%). The assay detected Mtb in stool of 7/7 children with smear-positive TB (100% sensitivity; 95% CI: 59–100%), and in 6/15 of children with smear-negative, culture-confirmed TB (40% sensitivity; 95% CI: 16–68%). Older age, smear positivity, culture positivity, ability to produce sputum and cavitary disease were associated with a positive stool result.

Conclusion

Testing of stool samples with the TruTip workstation and IS6110 amplification yielded sensitivity and specificity estimates comparable to other tests such as Xpert. Future work should include detection of resistance using the TruTip closed amplification system and assay optimization to improve sensitivity in children with low bacillary loads.

Diagnostic Accuracy of Stool Xpert MTB/RIF for Detection of Pulmonary Tuberculosis in Children: a Systematic Review and Meta-analysis

Invasive collection methods are often required to obtain samples for the microbiological evaluation of children with presumptive pulmonary tuberculosis (PTB). Nucleic acid amplification testing of easier-to-collect stool samples could be a noninvasive method of diagnosing PTB.

Invasive collection methods are often required to obtain samples for the microbiological evaluation of children with presumptive pulmonary tuberculosis (PTB). Nucleic acid amplification testing of easier-to-collect stool samples could be a noninvasive method of diagnosing PTB. We conducted a systematic review and meta-analysis to evaluate the diagnostic accuracy of testing stool with the Xpert MTB/RIF assay (“stool Xpert”) for childhood PTB. Four databases were searched for publications from January 2008 to June 2018. Studies assessing the diagnostic accuracy among children of stool Xpert compared to a microbiological reference standard of conventional specimens tested by mycobacterial culture or Xpert were eligible. Bivariate random-effects meta-analyses were performed to calculate pooled sensitivity and specificity of stool Xpert against the reference standard. From 1,589 citations, 9 studies (n = 1,681) were included. Median participant ages ranged from 1.3 to 10.6 years. Protocols for stool processing and testing varied substantially, with differences in reagents and methods of homogenization and filtering. Against the microbiological reference standard, the pooled sensitivity and specificity of stool Xpert were 67% (95% confidence interval [CI], 52 to 79%) and 99% (95% CI, 98 to 99%), respectively. Sensitivity was higher among children with HIV (79% [95% CI, 68 to 87%] versus 60% [95% CI, 44 to 74%] among HIV-uninfected children). Heterogeneity was high. Data were insufficient for subgroup analyses among children under the age of 5 years, the most relevant target population. Stool Xpert could be a noninvasive method of ruling in PTB in children, particularly those with HIV. However, studies focused on children under 5 years of age are needed, and generalizability of the evidence is limited by the lack of standardized stool preparation and testing protocols.

Recent Innovations in Diagnosis and Treatment of Pediatric Tuberculosis

PURPOSE OF REVIEW

Tuberculosis is leading cause of global morbidity and mortality and a significant proportion of the burden of disease occurs in children. In the past 5 years, a number of innovations have improved the diagnosis and treatment for children with both latent tuberculosis infection and active disease.

RECENT FINDINGS

This review discusses three key areas of innovation. First, we assess utilization and performance of interferon-gamma release assays (IGRAs) in different clinical and epidemiologic scenarios. Recent literature has demonstrated good performance of IGRAs for diagnosis of latent tuberculosis infection, particularly in low-incidence settings such as TB control programs in North America. For high-incidence populations, or when testing is done for possible active TB disease, IGRA performance has some important limitations, but IGRA sensitivity when measured against culture proven disease may be better than earlier studies suggested. The second area of innovation is in increased uptake of nucleic acid amplification (NAA) tests and broader application in non-sputum samples for both pediatric pulmonary and extrapulmonary tuberculosis. Finally, recent studies have provided solid evidence in support of shorter treatment courses for pediatric latent tuberculosis infection, such as 12 weeks of weekly isoniazid and rifapentine or 4 months daily rifampin, that improve compliance and may reduce resources required for TB control. Many recent innovations in pediatric tuberculosis relate to an improved understanding of how to optimally use existing tests and treatments. Until diagnostic tests and interventions such as vaccination are developed that can dramatically alter the paradigm of pediatric TB management and control, it is important for stakeholders to have a nuanced understanding of tools currently available.

Challenges and Progress with Diagnosing Pulmonary Tuberculosis in Low- and Middle-Income Countries

Case finding and the diagnosis of tuberculosis (TB) are key activities to reach the World Health Organization's End TB targets by 2030. This paper focuses on the diagnosis of pulmonary TB (PTB) in low- and middle-income countries. Sputum smear microscopy, despite its many limitations, remains the primary diagnostic tool in peripheral health facilities; however, this is being replaced by molecular diagnostic techniques, particularly Xpert MTB/RIF, which allows a bacteriologically confirmed diagnosis of TB along with information about whether or not the organism is resistant to rifampicin within two hours. Other useful diagnostic tools at peripheral facilities include chest radiography, urine lipoarabinomannan (TB-LAM) in HIV-infected patients with advanced immunodeficiency, and the loop-mediated isothermal amplification (TB-LAMP) test which may be superior to smear microscopy. National Reference Laboratories work at a higher level, largely performing culture and phenotypic drug susceptibility testing which is complemented by genotypic methods such as line probe assays for detecting resistance to isoniazid, rifampicin, and second-line drugs. Tuberculin skin testing, interferon gamma release assays, and commercial serological tests are not recommended for the diagnosis of active TB. Linking diagnosis to treatment and care is often poor, and this aspect of TB management needs far more attention than it currently receives.

Evaluation of Xpert MTB/RIF assay for detection of Mycobacterium tuberculosis in stool samples of adults with pulmonary tuberculosis

BACKGROUND

The Xpert MTB/RIF (Xpert) assay technology allows rapid and sensitive diagnosis of pulmonary tuberculosis (PTB) from sputum specimens. However, diagnosis of PTB is difficult for patients who cannot produce sputum. The objective of this study was to investigate the use of Xpert assay for successful detection of PTB using stool samples from adult subjects.

METHODS

Both stool and sputum samples from known smear and Xpert positive PTB patients were collected from a TB hospital in Dhaka. Stool samples were collected from healthy individuals without TB symptoms from a slum area of Dhaka. Stool and sputum samples were decontaminated and concentrated using NALC-NaOH-Na-citrate solution and the resultant sediment was used for Xpert, acid-fast bacilli (AFB) microscopy and culture.

RESULTS

A total of 102 stool samples were collected from PTB patients and another 50 stool samples from healthy individuals without TB. The sensitivity of the Xpert assay for detection of M. tuberculosis in stool samples of PTB patients was 90.2% (95% CI, 82.9-95.0). All 50 stool samples from healthy individuals were negative by the assay (Specificity 100%; 95% CI, 92.9-100). Compared with the sputum culture positive results the sensitivity of the stool Xpert assay was 94.8% (95% CI, 88.5-97.8). Moreover, stool Xpert demonstrated full concordant results with the sputum culture for detection of rifampicin susceptibility. The cycle threshold values of rpoB probes obtained from Xpert assay correlated significantly with the bacilli load in the corresponding stool (Spearman correlation = -0.40, P < 0.01) and sputum (Spearman correlation = -0.77, P < 0.01) samples as determined by microscopy.

CONCLUSIONS

Stool Xpert can be applied as a potential alternative of sputum testing for detection of M. tuberculosis and accurate determination of RIF susceptibility in adult PTB patients. The assay would be beneficial for rapid diagnosis of PTB for those adult patients who cannot expectorate sputum.

Molecular Detection of Mycobacterium tuberculosis from Stools in Young Children by Use of a Novel Centrifugation-Free Processing Method

The microbiological diagnosis of tuberculosis (TB) in children is challenging, as it relies on the collection of relatively invasive specimens by trained health care workers, which is not feasible in many settings. Mycobacterium tuberculosis is detectable from the stools of children using molecular methods, but processing stool specimens is resource intensive. We evaluated a novel, simple, centrifugation-free processing method for stool specimens for use on the Xpert MTB/RIF assay (Xpert), using two different stool masses: 0.6 g and a swab sample. Two hundred eighty children (median age, 15.5 months; 35 [12.5%] HIV infected) with suspected intrathoracic TB were enrolled from two sites in South Africa. Compared to a single Xpert test on respiratory specimens, the sensitivity of Xpert on stools using the 0.6-g and swab samples was 44.4% (95% confidence interval [CI], 13.7 to 78.8%) for both methods, with a specificity of >99%. The combined sensitivities of two stool tests versus the first respiratory Xpert were 70.0% (95% CI, 34.8 to 93.3) and 50.0% (95% CI, 18.7 to 81.3) for the 0.6-g and swab sample, respectively. Retesting stool specimens with nondeterminate Xpert results improved nondeterminate rates from 9.3% to 3.9% and from 8.6% to 4.3% for 0.6-g and swab samples, respectively. Overall, stool Xpert detected 14/94 (14.9%) children who initiated antituberculosis treatment, while respiratory specimens detected 23/94 (24.5%). This stool processing method is well suited for settings with low capacity for respiratory specimen collection. However, the overall sensitivity to detect confirmed and clinical TB was lower than that of respiratory specimens. More sensitive rapid molecular assays are needed to improve the utility of stools for the diagnosis of intrathoracic TB in children from resource-limited settings.

Stool Xpert MTB/RIF and urine lipoarabinomannan for the diagnosis of tuberculosis in hospitalized HIV-infected children

BACKGROUND

Tuberculosis (TB) causes substantial morbidity and mortality in HIV-infected children. Sample collection and the paucibacillary nature of TB in children makes diagnosis challenging. Rapid diagnostic tools using easily obtained specimens are urgently needed.

METHODS

Hospitalized, HIV-infected children aged 12 years or less enrolled in a randomized controlled trial (NCT02063880) comparing urgent to post-stabilization antiretroviral therapy initiation in Kenya underwent TB evaluation. At enrollment, sputum or gastric aspirates were collected for TB culture and Xpert, stool for Xpert, and urine for lipoarabinomannan (LAM). When possible, a second sputum/gastric aspirate for culture was obtained. Stool Xpert and urine LAM performance were compared to reference sputum/gastric aspirate culture.

RESULTS

Among 165 HIV-infected children, median age was 24 months [interquartile range (IQR) 13-58], median CD4% was 14.3 (IQR 8.9-22.0%), and 114 (69.5%) had severe immunosuppression. Thirteen (7.9%) children had confirmed TB (positive culture and/or Xpert). Sputum/gastric aspirate Xpert, stool Xpert, and urine LAM sensitivities were 60% [95% confidence interval (CI) 26-88%], 63% (95% CI 25-92%), and 43% (95% CI 10-82%), respectively. Specificity was 98% (95% CI 94-100%) for sputum/gastric aspirate Xpert, 99% (95% CI 95-100%) for stool Xpert, and 91% (95% CI 84-95%) for urine LAM. Stool Xpert and urine LAM sensitivity increased among children with severe immunosuppression [80% (95% CI 28-100) and 60% (95% Cl 15-95%)].

CONCLUSION

Stool Xpert had similar performance compared with sputum/gastric aspirate Xpert to detect TB. Urine LAM had lower sensitivity and specificity, but increased among children with severe immunosuppression. Stool Xpert and urine LAM can aid rapid detection of TB in HIV-infected children using easily accessible samples.

Evaluation of Xpert MTB/RIF testing for rapid diagnosis of childhood pulmonary tuberculosis in children by Xpert MTB/RIF testing of stool samples in a low resource setting

OBJECTIVE

Children with tuberculosis (TB) remain underdiagnosed due to difficulty in testing for Mycobacterium tuberculosis (MTB) infection. We evaluated the Xpert MTB/RIF assay for respiratory and stool testing in children for pulmonary TB through a cross-sectional study at tertiary care facilities in Karachi, Pakistan. Fifty children aged 0-15 years screened by a modified Kenneth-Jones (KJ) score were included. Mycobacterial culture of respiratory samples was the microbiological standard against stool Xpert TB results. All positive TB cases were compared against a treatment response standard (TRS).

RESULTS

Twelve study subjects were diagnosed by Xpert TB and nine by MTB culture. Compared with culture [gastric aspirates (GA)/sputum (spm)], stool Xpert TB had a sensitivity of 88.9% (95% CI 50.7-99.4) and a specificity of 95% (95% CI 81.8-99.1). Xpert TB stool versus GA/spm had sensitivity of 81.8% (95% CI 47.8-96.8) and specificity of 94.7% (95% CI 84.6-99.9). We found good agreement (kappa scores of >0.8) between stool Xpert, GA/spm Xpert and GA/spm culture. Stool Xpert PPV and NPV against TRS was 100 and 82.1% respectively. Stool Xpert TB is a relatively easy option for diagnosis for pulmonary childhood TB in a high burden low-resource setting.