Promising directions in the diagnosis of childhood tuberculosis

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.

Advances in the diagnosis, treatment, and prevention of tuberculosis in children

INTRODUCTION

Pediatric tuberculosis (TB) is a significant global health threat and is one of the top ten causes of death in children. There are a number of diagnostic, treatment, and preventive innovations that have been developed in the last decade for TB, however, these are out of reach for many children in the world. Areas covered: A comprehensive review of the literature on TB in children was done using PubMed and Ovid databases from 1 January 1996 up to 31 October 2018. Topic areas covered included diagnosis of TB, treatment of TB (including novel medications and regimens), prevention of DR-TB, and support to achieve the best possible outcomes. Each of these areas are explored in more detail in the paper. Expert commentary: There is great potential for radical changes in the way all forms of TB are diagnosed, treated and prevented in children. If there is continued advocacy and adequate funding and accountability, it could be possible to make great strides toward eliminating TB in children in the next ten years.

CD163 levels, pro- and anti-inflammatory cytokine secretion of monocytes in children with pulmonary tuberculosis

OBJECTIVES

Childhood tuberculosis (TB) comprises an important part of the world's TB burden. Monocytes set up the early phase of infection because of innate immune responses. Understanding the changes in monocyte subsets during multisystem infectious diseases may be important for the development of novel diagnostic and therapeutic strategies. The aim of this study was to evaluate the monocyte phenotype together with the cytokine secretion profiles of children with pulmonary tuberculosis.

STUDY DESIGN

Thirteen patients with pulmonary TB were enrolled as study group, and 14 healthy subjects as control group. Surface expressions of CD16, CD14, CD62L, CD163, CCR2, and HLA-DR of monocytes were analyzed by flow cytometry. The presence of IFN-γ, TNF-α, IL-10, IL-12, IL-23, and soluble form of CD163 (sCD163) in the antigen- and LPS-stimulated whole blood culture supernatants were detected using ELISA and Luminex.

RESULTS

Higher percentages of CD14⁺⁺ CD16⁺ and CD14⁺ CD16⁺⁺ monocyte subsets, and CCR2, CD62L and CD163 expression on circulating monocytes in children with pulmonary tuberculosis were obtained. Diminished levels of ESAT-6/CFP-10-induced IL-10 and increased levels of TB-antigen and LPS-stimulated sCD163 were found in childhood with pulmonary TB.

CONCLUSIONS

High expression of CD14⁺⁺ CD16⁺ , CD14⁺ CD16⁺⁺ , CD14⁺ CCR2⁺ , and CD14⁺ CD62L⁺ cells in childhood TB, and monocyte-derived cytokines reflected both pro- and anti-inflammatory profiles. Higher sCD163 and CD14⁺ CD163⁺ monocytes might help physicians in the differential diagnosis of pulmonary TB in children. Pediatr Pulmonol. 2017;52:675-683. © 2016 Wiley Periodicals, Inc.

Evaluation of the Xpert MTB/RIF assay in gastric lavage aspirates for diagnosis of smear-negative childhood pulmonary tuberculosis

BACKGROUND

The diagnosis of pulmonary tuberculosis (TB) in children presents problems worldwide. The Xpert MTB/RIF assay serves as a useful alternative for the rapid diagnosis of childhood TB, with various clinical specimens.

METHODS

In this study, we evaluated the Xpert for diagnosis of smear-negative childhood pulmonary TB using gastric lavage aspirates (GLA). A total of 211 eligible children with suspected TB were consecutively recruited and had GLA obtained for analysis between October 2012 and October 2013 in Beijing Children's Hospital.

RESULTS

The percentages of TB children in <1 year [Odds ratio (95% confidence interval): 4.66 (1.81-11.97)], >5 years group [2.59 (1.30-5.16)] and of living in a rural region [3.78 (2.02-7.08)] were significantly higher than in control groups. The sensitivity in detecting children with a clinical diagnosis of TB for MGIT and Xpert was 12.1% (95% confidence interval: 9.3-14.9%) and 48.6% (95% confidence interval: 44.4-52.8%), respectively. The statistical analysis revealed that GeneXpert showed significantly better sensitivity than MGIT technology (P < 0.001).

CONCLUSIONS

We conclude that Xpert MTB/RIF assay is an excellent tool for the diagnosis of smear-negative childhood with GLA samples. The high proportion of very low mycobacterial load in the GLA samples from smear-negative TB cases may increase the frequency for obtaining indeterminate RIF resistance results by Xpert. In addition, the age <1 year, >5 years and living in a rural region are all high risk factors for childhood TB cases in China.

Diagnosis of childhood tuberculosis and host RNA expression in Africa

BACKGROUND

Improved diagnostic tests for tuberculosis in children are needed. We hypothesized that transcriptional signatures of host blood could be used to distinguish tuberculosis from other diseases in African children who either were or were not infected with the human immunodeficiency virus (HIV).

METHODS

The study population comprised prospective cohorts of children who were undergoing evaluation for suspected tuberculosis in South Africa (655 children), Malawi (701 children), and Kenya (1599 children). Patients were assigned to groups according to whether the diagnosis was culture-confirmed tuberculosis, culture-negative tuberculosis, diseases other than tuberculosis, or latent tuberculosis infection. Diagnostic signatures distinguishing tuberculosis from other diseases and from latent tuberculosis infection were identified from genomewide analysis of RNA expression in host blood.

RESULTS

We identified a 51-transcript signature distinguishing tuberculosis from other diseases in the South African and Malawian children (the discovery cohort). In the Kenyan children (the validation cohort), a risk score based on the signature for tuberculosis and for diseases other than tuberculosis showed a sensitivity of 82.9% (95% confidence interval [CI], 68.6 to 94.3) and a specificity of 83.6% (95% CI, 74.6 to 92.7) for the diagnosis of culture-confirmed tuberculosis. Among patients with cultures negative for Mycobacterium tuberculosis who were treated for tuberculosis (those with highly probable, probable, or possible cases of tuberculosis), the estimated sensitivity was 62.5 to 82.3%, 42.1 to 80.8%, and 35.3 to 79.6%, respectively, for different estimates of actual tuberculosis in the groups. In comparison, the sensitivity of the Xpert MTB/RIF assay for molecular detection of M. tuberculosis DNA in cases of culture-confirmed tuberculosis was 54.3% (95% CI, 37.1 to 68.6), and the sensitivity in highly probable, probable, or possible cases was an estimated 25.0 to 35.7%, 5.3 to 13.3%, and 0%, respectively; the specificity of the assay was 100%.

CONCLUSIONS

RNA expression signatures provided data that helped distinguish tuberculosis from other diseases in African children with and those without HIV infection. (Funded by the European Union Action for Diseases of Poverty Program and others).

Impact of human immunodeficiency virus and CD4 count on tuberculosis diagnosis: analysis of city-wide data from Cape Town, South Africa

BACKGROUND

The impact of human immunodeficiency virus (HIV) infection and CD4 count on the diagnosis of tuberculosis (TB) at population level is incompletely defined.

OBJECTIVE

To determine how HIV infection and CD4 count affect disease site, sputum smear status and overall rate of laboratory confirmation (sputum smear microscopy or culture) of TB cases under routine programme conditions.

DESIGN

Retrospective analysis of the 2009 electronic TB register for Cape Town, South Africa.

RESULTS

Of 29,478 TB cases notified in 2009, HIV status was known for 25,744 (87.3%) cases, of whom 13,237 (51.4%) were HIV-positive. Of these, 61.2% had CD4 cell counts of <200 cells/μl and 82.7% had counts of <350 cells/μl. Laboratory confirmation of TB (by smear or culture) was obtained less frequently in HIV-infected than non-HIV-infected adult cases (53.9% vs. 74.3%, P< 0.001). HIV infection was associated with a higher proportion of sputum smear-negative and extra-pulmonary TB and lower grades of sputum smear positivity even among those with CD4 counts of ≥ 500 cells/μl. However, the relationship between the proportion of smear-positive cases and CD4 count was non-linear.

CONCLUSION

Much TB is not laboratory-confirmed in this setting despite good laboratory services. HIV-associated TB is more difficult to diagnose even at high CD4 cell counts of >500 cells/μl, suggesting early impact after HIV seroconversion.

Tuberculosis and HIV co-infection in children

HIV is the top and tuberculosis is the second leading cause of death from infectious disease worldwide, with an estimated 8.7 million incident cases of tuberculosis and 2.5 million new HIV infections annually. The World Health Organization estimates that HIV prevalence among children with tuberculosis, in countries with moderate to high prevalence, ranges from 10 to 60%. The mechanisms promoting susceptibility of people with HIV to tuberculosis disease are incompletely understood, being likely caused by multifactorial processes. Paediatric tuberculosis and HIV have overlapping clinical manifestations, which could lead to missed or late diagnosis. Although every effort should be made to obtain a microbiologically-confirmed diagnosis in children with tuberculosis, in reality this may only be achieved in a minority, reflecting their paucibacillary nature and the difficulties in obtain samples. Rapid polymerase chain reaction tests, such as Xpert MTB/RIF assay, are increasingly used in children. The use of less or non invasive methods of sample collection, such as naso-pharyngeal aspirates and stool samples for a polymerase chain reaction-based diagnostic test tests and mycobacterial cultures is promising technique in HIV negative and HIV positive children. Anti-tuberculosis treatment should be started immediately at diagnosis with a four drug regimen, irrespective of the disease severity. Moreover, tuberculosis disease in an HIV infected child is considered to be a clinical indication for initiation of antiretroviral treatment. The World Health Organization recommends starting antiretroviral treatment in children as soon as anti-tuberculosis treatment is tolerated and within 2- 8 weeks after initiating it. The treatment of choice depends on the child's age and availability of age-appropriate formulations, and potential drug interactions and resistance. Treatment of multidrug resistant tuberculosis in HIV-infected children follows same principles as for HIV uninfected children. There are conflicting results on effectiveness of isoniazid preventive therapy in reducing incidence of tuberculosis disease in children with HIV.

CONCLUSION

Data on HIV/TB co-infection in children are still lacking. There are on-going large clinical trials on the prevention and treatment of TB/HIV infection in children that hopefully will help to guide an evidence-based clinical practice in both resource-rich and resource-limited settings.HIV is the top and tuberculosis is the second leading cause of death from infectious disease worldwide, with an estimated 8.7 million incident cases of tuberculosis and 2.5 million new HIV infections annually. The World Health Organization estimates that HIV prevalence among children with tuberculosis, in countries with moderate to high prevalence, ranges from 10 to 60%. The mechanisms promoting susceptibility of people with HIV to tuberculosis disease are incompletely understood, being likely caused by multifactorial processes.

Diagnosis of pulmonary tuberculosis

PURPOSE OF REVIEW

This review summarizes the recent literature on the developments in diagnostics for pulmonary tuberculosis (TB).

RECENT FINDINGS

A growing body of literature regarding the Xpert MTB/RIF assay confirms the high diagnostic accuracy in a range of clinical settings, including amongst inpatients, those with HIV coinfection and in children with culture-positive disease. Early experiences with operational implementation are now being reported from South Africa. Initial small-scale evaluations suggest that newer versions of line-probe assays have diagnostic accuracy similar to that of the Xpert MTB/RIF assay. Next-generation fully automated molecular assays that use isothermal amplification may in the future be more readily implemented at the point of care. The first low-cost, lateral-flow (strip-test) assay for lipoarabinomannan in urine shows promise as a rapid point-of-care test for TB amongst HIV-infected patients who have advanced immunodeficiency. A range of other diagnostic tools are also at various stages of development.

SUMMARY

There is continued momentum and optimism regarding the developments in TB diagnostics. However, studies of clinical and programmatic impact and operational research are needed to guide implementation and scale-up of new assays in resource-limited settings. Further concerted efforts are needed to develop point-of-care assays which are desperately needed to accelerate progress in TB control.