Accuracy of Lipoarabinomannan and Xpert MTB/RIF Testing in Cerebrospinal Fluid To Diagnose Tuberculous Meningitis in an Autopsy Cohort of HIV-Infected Adults

Diagnostic accuracy of Lipoarabinomannan detection by lateral flow assay in pleural tuberculosis

BACKGROUND

Lipoarabinomannan (LAM) antigen serves as an attractive biomarker to diagnose Tuberculosis (TB). Given the limitations of current diagnostic modalities for Pleural TB, current study evaluated LAM's potential to serve as a point-of-care test to diagnose pleural TB.

METHODS

A cross sectional, diagnostic accuracy study was conducted during February to November 2021 in a tertiary care hospital in India. LAM antigen detection was performed on pleural fluid as well as early morning urine specimen of suspected pleural TB patients by "Alere/ Abott Determine TB LAM" lateral flow assay (LAM-LFA). The results were compared to microbiological reference standards/MRS (Mycobacterial culture or NAAT) and Composite reference standards/CRS (MRS plus Clinico-radiological diagnosis).

RESULTS

A total of 170 subjects were included in the analysis, including 26 with Definite TB, 22 with Probable TB, and 122 with No TB. Compared to MRS and CRS, the sensitivity (61.54% & 45.83%) and positive predictive value (PPV) (57.14 & 78.57%) of Pleural LAM-LFA testing were found to be suboptimal, whereas the specificity (91.67% & 95.08%) and negative predictive value (NPV) (92.96% & 81.69%) of the assay were found to be good. Urinary LAM-LFA performed even worse than pleural LAM-LFA, except for its higher specificity against MRS and CRS (97.2% and 98.3%, respectively). Specificity and PPV of pleural LAM detection increased to 100% when analysed in a subgroup of patients with elevated ADA levels (receiver operating curve analysis-derived cut off value > 40 IU/ml).

CONCLUSION

Detection of LAM antigen by LFA directly from pleural fluid was found to be a useful test to predict absence of the disease if the test is negative rather than using as a POCT for diagnosis.

Diagnostic value of the cerebrospinal fluid lipoarabinomannan assay for tuberculous meningitis: a systematic review and meta-analysis

Objective

This systematic review aims to evaluate the diagnostic accuracy of cerebrospinal fluid (CSF) lipoarabinomannan (LAM) assays in detecting tuberculous meningitis (TBM).

Methods

A systematic review search was conducted in PubMed and five other databases up to April 2023. Studies that evaluated the diagnostic accuracy of CSF LAM assays were included with either definitive or composite reference standard used as the preferred reference standard. The quality of the included studies was assessed using the QUADAS-2 tool. We performed a bivariate random-effects meta-analysis and calculated the summary diagnostic statistics.

Results

A total of six studies, including a sample size of 999, were included in the final analysis. The pooled sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) of CSF LAM for diagnosing TBM were determined to be 0.44 (95% CI: 0.31-0.58), 0.89 (95% CI: 0.81-0.93), and 0.76 (95% CI: 0.73-0.80), respectively. Significant heterogeneity was observed in both sensitivity (Q = 73.82, p < 0.01; I2 = 86.45, 95%CI: 79.64-93.27) and specificity (Q = 95.34, p < 0.01; I2 = 89.51, 95% CI: 84.61-94.42). Regression analysis indicated that the study design (retrospective vs. prospective) was associated with the heterogeneity of pooled sensitivity and specificity (all p < 0.05).

Conclusion

Although more prospective studies are required to validate the role of the CSF LAM assay, current evidence supports that the performance of the CSF LAM assay is unsatisfactory for the TBM diagnosis. Additionally, the optimization of the CSF LAM assay (e.g., improvements in CSF collection and preparation methods) should be considered to improve its performance.

Fujifilm SILVAMP TB LAM Assay on Cerebrospinal Fluid for the Detection of Tuberculous Meningitis in Adults With Human Immunodeficiency Virus

BACKGROUND

Tuberculous meningitis (TBM) has a high fatality rate, with inadequate diagnostic tests being a major contributor. The rollout of Xpert MTB/Rif and Xpert MTB/RIF Ultra (Xpert Ultra) have improved time-to-diagnosis with sensitivities similar to culture, yet test availability and sensitivity are inadequate. The TB lipoarabinomannan lateral flow assay (AlereLAM) offers ease of use, but its low sensitivity in cerebrospinal fluid (CSF) limits clinical utility for TBM. The Fujifilm SILVAMP TB LAM (FujiLAM) assay has excellent sensitivity in urine, but performance on cerebrospinal fluid is uncertain.

METHODS

We conducted a prospective cohort study at Kiruddu National Referral Hospital in Kampala, Uganda, enrolling patients suspected to have TBM. CSF was tested using AlereLAM, Xpert Ultra, culture, and FujiLAM. Results were compared with 2 reference standards: probable and definite TBM or definite TBM alone by the uniform TBM case definition.

RESULTS

Of 101 patients enrolled (95/101 HIV-positive), 34 had definite TBM and 24 had probable TBM. FujiLAM sensitivity on CSF was 52% (30/58) for definite or probable TBM compared with 55% (32/58) for Xpert Ultra. AlereLAM had lower sensitivity than FujiLAM in the subgroup of patients tested with both assays (14% [4/28] vs 50% [14/28]; P < .01). FujiLAM specificity was 98% (42/43) for patients without probable or definite TBM.

CONCLUSIONS

FujiLAM showed higher sensitivity than AlereLAM, with sensitivity potentially approaching that of Xpert Ultra. FujiLAM could improve time-to-treatment-initiation, especially in settings where the more technical Xpert Ultra system might not be feasible. Large confirmatory studies are needed.

Early Empirical Tuberculosis Treatment in HIV-Positive Patients Admitted to Hospital in South Africa: An Observational Cohort Study

BACKGROUND

Empirical tuberculosis (TB) treatment in human immunodeficiency virus (HIV)-positive inpatients is common and may undermine the impact of new diagnostics. We sought to describe empirical TB treatment and compare characteristics and outcomes with patients treated for TB after screening.

METHODS

This was a retrospective observational cohort study of HIV-positive inpatients treated empirically for TB prior to TB screening. Data on clinical characteristics, investigations, and outcomes were collected from medical records. Comparison cohorts with microbiologically confirmed or empirical TB treatment after TB screening with Xpert MTB/RIF and urine lipoarabinomannan assays were taken from South African Screening for Tuberculosis to Reduce AIDS-Related Mortality in Hospitalized Patients in Africa (STAMP) trial site. In-hospital mortality was compared using a competing-risks analysis adjusted for age, sex, and CD4 cell count.

RESULTS

Between January 2016 and September 2017, 100 patients excluded from STAMP were treated for TB empirically prior to TB screening. After enrollment in STAMP and TB screening, 240 of 1177 (20.4%) patients received TB treatment, of whom 123 had positive TB tests and 117 were treated empirically. Characteristics were similar among early empirically treated patients and those treated after TB screening. 50% of early empirical TB treatment was based on radiological investigations, 22% on cerebrospinal or pleural fluid testing, and 28% on clinical features alone. Only 11 of 100 empirically treated patients had subsequent microbiological confirmation. In-hospital mortality was lower in patients with microbiologically confirmed TB compared to those treated empirically (adjusted subdistribution hazard ratio, 0.5 [95% confidence interval, .3-.9).

CONCLUSIONS

Empirical TB treatment remains common in severely ill HIV-positive inpatients. These patients may benefit from TB screening using existing rapid diagnostics, both to improve confirmation of TB disease and reduce overtreatment for TB.

Strategies for the diagnosis and management of meningitis in HIV-infected adults in resource limited settings

INTRODUCTION

The incidence of human immunodeficiency virus-1 (HIV-1) associated meningitis has been declining in the post-combination antiretroviral treatment (ART) era, although survival rates remain low for the common causes like tuberculosis and cryptococcal disease. Diagnosis and treatment of meningitis in HIV-1 is complicated by atypical clinical presentations, limited accuracy of diagnostic tests, access to diagnostic tests, and therapeutic agents in low- and middle-income countries (LMIC) and immune reconstitution inflammatory syndrome (IRIS).

AREAS COVERED

We provide an overview of the common etiologies of meningitis in HIV-1-infected adults, suggest a diagnostic approach based on readily available tests, and review specific chemotherapeutic agents, host-directed therapies, supportive care, timing of ART initiation, and considerations in the management of IRIS with a focus on resource-limited settings. They identify key knowledge gaps and suggest areas for future research.

EXPERT OPINION

Evidence-based management of HIV-1-associated meningitis is sparse for common etiologies. More readily available and sensitive diagnostic tests as well as standardized investigation strategies are required in LMIC. There is a lack of availability of recommended drugs in areas of high HIV-1 prevalence and a limited pipeline of novel chemotherapeutic agents. Host-directed therapies have been inadequately studied.

Recent Developments in Tuberculous Meningitis Pathogenesis and Diagnostics

The pathogenesis of Tuberculous meningitis (TBM) is poorly understood, but contemporary molecular biology technologies have allowed for recent improvements in our understanding of TBM. For instance, neutrophils appear to play a significant role in the immunopathogenesis of TBM, and either a paucity or an excess of inflammation can be detrimental in TBM. Further, severity of HIV-associated immunosuppression is an important determinant of inflammatory response; patients with the advanced immunosuppression (CD4+ T-cell count of <150 cells/μL) having higher CSF neutrophils, greater CSF cytokine concentrations and higher mortality than those with CD4+ T-cell counts > 150 cells/μL. Host genetics may also influence outcomes with LT4AH genotype predicting inflammatory phenotype, steroid responsiveness and survival in Vietnamese adults with TBM. Whist in Indonesia, CSF tryptophan level was a predictor of survival, suggesting tryptophan metabolism may be important in TBM pathogenesis. These varying responses mean that we must consider whether a "one-size-fits-all" approach to anti-bacillary or immunomodulatory treatment in TBM is truly the best way forward. Of course, to allow for proper treatment, early and rapid diagnosis of TBM must occur. Diagnosis has always been a challenge but the field of TB diagnosis is evolving, with sensitivities of at least 70% now possible in less than two hours with GeneXpert MTB/Rif Ultra. In addition, advanced molecular techniques such as CRISPR-MTB and metagenomic next generation sequencing may hold promise for TBM diagnosis. Host-based biomarkers and signatures are being further evaluated in childhood and adult TBM as adjunctive biomarkers as even with improved molecular assays, cases are still missed. A better grasp of host and pathogen behaviour may lead to improved diagnostics, targeted immunotherapy, and possibly biomarker-based, patient-specific treatment regimens.

A comparison of the accuracy of the CapitalBio Mycobacterium real-time polymerase chain reaction and the Xpert MTB/RIF assay for the diagnosis of tuberculous meningitis

OBJECTIVES

We aimed to compare the efficiency of the CapitalBioMycobacterium real-time polymerase chain reaction (PCR) detection test with the standard Xpert MTB/RIF assay for the diagnosis of tuberculous meningitis (TBM).

METHODS

We analyzed cerebrospinal fluid (CSF) from 163 patients with suspected TBM that were collected between January 1, 2018, and December 31, 2019. For both tests, we determined the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC). Next, we compared the diagnostic accuracy of the two techniques using clinical diagnosis as a reference standard.

RESULTS

The sensitivity, specificity, PPV, NPV, and AUC, of the CapitalBio Mycobacterium detection test were 48.5%, 100%, 100%, 29.6%, and 0.74, respectively, when used for the diagnosis of TBM. In comparison, the Xpert MTB/RIF assay returned values of 47.0%, 100%, 100%, 29.0%, and 0.74, respectively. Our analysis showed that the diagnostic accuracies of the CapitalBio Mycobacterium detection test and the Xpert MTB/RIF assay were very similar; the accuracy of both tests for detecting mycobacteria was significantly higher than that associated with acid-fast staining.

CONCLUSIONS

The CapitalBio Mycobacterium real-time PCR detection test has moderate sensitivity and very high specificity for TBM; results are very similar to those generated by the Xpert MTB/RIF assay. We recommend that the CapitalBio PCR test should be used as an initial screening method for TB.

Comparison of the efficacy of metagenomic next-generation sequencing and Xpert MTB/RIF in the diagnosis of tuberculous meningitis

Metagenomic next-generation sequencing (mNGS) is an emerging sequence-based method that detects genomic information of pathogenic microorganisms from a wide range of clinical specimens. The mNGS has moderate sensitivity and very high specificity for tuberculous meningitis, and the validity of mNGS was higher than that of Xpert MTB/RIF.

Diagnostic accuracy of Xpert MTB/RIF for tuberculous meningitis: systematic review and meta-analysis

OBJECTIVE

This systematic review evaluated the diagnostic accuracy of Xpert MTB/RIF to detect tuberculous meningitis (TBM).

METHODS

PubMed and five other databases were systematically searched through March 2019. All studies evaluating diagnostic accuracy of Xpert MTB/RIF on cerebrospinal fluid (CSF) samples were included. Reference standards were definitive or definite plus probable TBM. The quality of studies was assessed by the QUADAS-2 tool. We performed bivariate random-effects meta-analysis and calculated summary diagnostic statistics.

RESULTS

We identified 30 studies (n = 3972 participants), including 5 cohort studies and 25 cross-sectional studies. Reference standards were definite TB (n = 28 studies) or definite plus probable TBM (n = 6 studies). The pooled Xpert MTB/RIF sensitivity was 85% (95% CI, 70-93%), and specificity was 98% (95% CI, 97-99%) with a negative likelihood ratio of 0.15 (95% CI, 0.04-0.27) for definite TBM. For probable TBM cases, pooled sensitivity was 81% (95% CI, 66-90%), and specificity was 99% (95% CI, 97-99%). For both reference standard types, meta-analyses showed a C-statistic area under the curve of 0.98. The QUADAS-2 tool revealed low risk of bias as well as low concerns regarding applicability. Methodological heterogeneity was high among studies.

CONCLUSIONS

Xpert MTB/RIF showed high accuracy for TBM diagnosis, but a negative Xpert MTB/RIF test does not rule out TBM. Repeat Xpert testing may be necessary. In clinical practice, Xpert MTB/RIF adds speed and sensitivity when compared to classic TBM diagnostic methods or previous commercial nucleic acid amplification techniques. More studies and better strategies for rapidly confirming a diagnosis of TBM in children are urgently needed.

Challenges in the diagnosis of tuberculous meningitis

Tuberculosis (TB) continues to pose a significant public health problem. Tuberculous meningitis (TBM) is the most severe form of extra-pulmonary TB. TBM carries a high mortality rate, including for those receiving treatment for TB. Diagnosis of TBM is difficult for clinicians as it can clinically present similarly to other forms of meningitis. The difficulty in diagnosis often leads to a delay in treatment and subsequent mortality. Those who survive are left with long-term sequelae leading to lifelong disability. The microbiologic diagnosis of TBM requires the isolation of Mycobacterium tuberculosis from the cerebrospinal fluid (CSF) of an infected patient. The diagnosis of tuberculous meningitis continues to be challenging for clinicians. Unfortunately, many cases of TBM cannot be confirmed based on clinical and imaging findings as the clinical findings are nonspecific, while laboratory techniques are largely insensitive or slow. Until recently, the lack of accessible and timely tests has contributed to a delay in diagnosis and subsequent morbidity and mortality for many patients, particularly those in resourcelimited settings. The availability of Xpert Ultra and point-of-care lipoarabinomannan (LAM) testing could represent a new era of prompt diagnosis and early treatment of tuberculous meningitis. However, clinicians must be cautious when ruling out TBM with Xpert Ultra due to its low negative predictive value. Due to the limitations of current diagnostics, clinicians should utilize a combination of diagnostic modalities in order to prevent morbidity in patients with TBM.

Recent Developments in Tuberculous Meningitis Pathogenesis and Diagnostics

The pathogenesis of Tuberculous meningitis (TBM) is poorly understood, but contemporary molecular biology technologies have allowed for recent improvements in our understanding of TBM. For instance, neutrophils appear to play a significant role in the immunopathogenesis of TBM, and either a paucity or an excess of inflammation can be detrimental in TBM. Further, severity of HIV-associated immunosuppression is an important determinant of inflammatory response; patients with the advanced immunosuppression (CD4+ T-cell count of <150 cells/μL) having higher CSF neutrophils, greater CSF cytokine concentrations and higher mortality than those with CD4+ T-cell counts > 150 cells/μL. Host genetics may also influence outcomes with LT4AH genotype predicting inflammatory phenotype, steroid responsiveness and survival in Vietnamese adults with TBM. Whist in Indonesia, CSF tryptophan level was a predictor of survival, suggesting tryptophan metabolism may be important in TBM pathogenesis. These varying responses mean that we must consider whether a "one-size-fits-all" approach to anti-bacillary or immunomodulatory treatment in TBM is truly the best way forward. Of course, to allow for proper treatment, early and rapid diagnosis of TBM must occur. Diagnosis has always been a challenge but the field of TB diagnosis is evolving, with sensitivities of at least 70% now possible in less than two hours with GeneXpert MTB/Rif Ultra. In addition, advanced molecular techniques such as CRISPR-MTB and metagenomic next generation sequencing may hold promise for TBM diagnosis. Host-based biomarkers and signatures are being further evaluated in childhood and adult TBM as adjunctive biomarkers as even with improved molecular assays, cases are still missed. A better grasp of host and pathogen behaviour may lead to improved diagnostics, targeted immunotherapy, and possibly biomarker-based, patient-specific treatment regimens.

Overview of Brain-to-Gut Axis Exposed to Chronic CNS Bacterial Infection(s) and a Predictive Urinary Metabolic Profile of a Brain Infected by Mycobacterium tuberculosis

A new paradigm in neuroscience has recently emerged - the brain-gut axis (BGA). The contemporary focus in this paradigm has been gut → brain ("bottom-up"), in which the gut-microbiome, and its perturbations, affects one's psychological state-of-mind and behavior, and is pivotal in neurodegenerative disorders. The emerging brain → gut ("top-down") concept, the subject of this review, proposes that dysfunctional brain health can alter the gut-microbiome. Feedback of this alternative bidirectional highway subsequently aggravates the neurological pathology. This paradigm shift, however, focuses upon non-communicable neurological diseases (progressive neuroinflammation). What of infectious diseases, in which pathogenic bacteria penetrate the blood-brain barrier and interact with the brain, and what is this effect on the BGA in bacterial infection(s) that cause chronic neuroinflammation? Persistent immune activity in the CNS due to chronic neuroinflammation can lead to irreversible neurodegeneration and neuronal death. The properties of cerebrospinal fluid (CSF), such as immunological markers, are used to diagnose brain disorders. But what of metabolic markers for such purposes? If a BGA exists, then chronic CNS bacterial infection(s) should theoretically be reflected in the urine. The premise here is that chronic CNS bacterial infection(s) will affect the gut-microbiome and that perturbed metabolism in both the CNS and gut will release metabolites into the blood that are filtered (kidneys) and excreted in the urine. Here we assess the literature on the effects of chronic neuroinflammatory diseases on the gut-microbiome caused by bacterial infection(s) of the CNS, in the context of information attained via metabolomics-based studies of urine. Furthermore, we take a severe chronic neuroinflammatory infectious disease - tuberculous meningitis (TBM), caused by Mycobacterium tuberculosis, and examine three previously validated CSF immunological biomarkers - vascular endothelial growth factor, interferon-gamma and myeloperoxidase - in terms of the expected changes in normal brain metabolism. We then model the downstream metabolic effects expected, predicting pivotal altered metabolic pathways that would be reflected in the urinary profiles of TBM subjects. Our cascading metabolic model should be adjustable to account for other types of CNS bacterial infection(s) associated with chronic neuroinflammation, typically prevalent, and difficult to distinguish from TBM, in the resource-constrained settings of poor communities.

Methods for rapid diagnosis of meningitis etiology in adults

Infectious meningitis can be caused by viral, bacterial or fungal pathogens. Despite widely available treatments, many types of infectious meningitis are still associated with significant morbidity and mortality. Delay in diagnosis contributes to poor outcomes. Cerebrospinal fluid cultures have been used traditionally but are time intensive and sensitivity is decreased by empiric treatment prior to culture. More rapid techniques such as the cryptococcal lateral flow assay (IMMY), GeneXpert MTB/Rif Ultra (Cepheid) and FilmArray multiplex-PCR (Biofire) are three examples that have drastically changed meningitis diagnostics. This review will discuss a holistic approach to diagnosing bacterial, mycobacterial, viral and fungal meningitis.

Recent Developments in Tuberculous Meningitis Pathogenesis and Diagnostics

The pathogenesis of Tuberculous meningitis (TBM) is poorly understood, but contemporary molecular biology technologies have allowed for recent improvements in our understanding of TBM. For instance, neutrophils appear to play a significant role in the immunopathogenesis of TBM, and either a paucity or an excess of inflammation can be detrimental in TBM. Further, severity of HIV-associated immunosuppression is an important determinant of inflammatory response; patients with the advanced immunosuppression (CD4+ T-cell count of <150 cells/μL) having higher CSF neutrophils, greater CSF cytokine concentrations and higher mortality than those with CD4+ T-cell counts > 150 cells/μL. Host genetics may also influence outcomes with LT4AH genotype predicting inflammatory phenotype, steroid responsiveness and survival in Vietnamese adults with TBM. Whist in Indonesia, CSF tryptophan level was a predictor of survival, suggesting tryptophan metabolism may be important in TBM pathogenesis. These varying responses mean that we must consider whether a "one-size-fits-all" approach to anti-bacillary or immunomodulatory treatment in TBM is truly the best way forward. Of course, to allow for proper treatment, early and rapid diagnosis of TBM must occur. Diagnosis has always been a challenge but the field of TB diagnosis is evolving, with sensitivities of at least 70% now possible in less than two hours with GeneXpert MTB/Rif Ultra. In addition, advanced molecular techniques such as CRISPR-MTB and metagenomic next generation sequencing may hold promise for TBM diagnosis. Host-based biomarkers and signatures are being further evaluated in childhood and adult TBM as adjunctive biomarkers as even with improved molecular assays, cases are still missed. A better grasp of host and pathogen behaviour may lead to improved diagnostics, targeted immunotherapy, and possibly biomarker-based, patient-specific treatment regimens.

Performance of Lipoarabinomannan Assay using Cerebrospinal fluid for the diagnosis of Tuberculous meningitis among HIV patients

Background: The diagnostic utility of the Mycobacteria tuberculosis lipoarabinomannan (TB-LAM) antigen lateral flow assay on cerebrospinal fluid (CSF) for the diagnosis of tuberculous meningitis (TBM) has not been extensively studied and the few published studies have conflicting results. Methods: Lumbar CSF from 59 HIV-positive patients with suspected TBM was tested with TB-LAM and Xpert MTB/Rif Ultra. The diagnostic performance of CSF TB-LAM was compared to positive CSF Xpert MTB/Rif Ultra (definite TBM) and a composite reference of probable or definite TBM according to the uniform case definition.  Results: Of 59 subjects, 12 (20%) had definite TBM and five (9%) had probable TBM. With reference to definite TBM, CSF TB-LAM assay had a diagnostic sensitivity of 33% and specificity of 96%. When compared to a composite reference of definite or probable TBM, the sensitivity was 24% and specificity was 95%. There were two false positive tests with TB-LAM (3+ grade). In-hospital mortality in CSF TB-LAM positive patients was 17% compared to 0% in those with definite TBM by Xpert MTB/Rif Ultra but negative LAM. Conclusions: Lumbar CSF TB-LAM has a poor performance in diagnosing TBM. Both urine TB-LAM and Xpert Ultra should be further investigated in the diagnosis of TBM.

Performance of Lipoarabinomannan Assay using Cerebrospinal fluid for the diagnosis of Tuberculous meningitis among HIV patients

Background: The diagnostic utility of the Mycobacteria tuberculosis lipoarabinomannan (TB-LAM) antigen lateral flow assay on cerebrospinal fluid (CSF) for the diagnosis of tuberculous meningitis (TBM) has not been extensively studied and the few published studies have conflicting results. Methods: Lumbar CSF from 59 HIV-positive patients with suspected TBM was tested with TB-LAM and Xpert MTB/Rif Ultra. The diagnostic performance of CSF TB-LAM was compared to positive CSF Xpert MTB/Rif Ultra (definite TBM) and a composite reference of probable or definite TBM according to the uniform case definition.  Results: Of 59 subjects, 12 (20%) had definite TBM and five (9%) had probable TBM. With reference to definite TBM, CSF TB-LAM assay had a diagnostic sensitivity of 33% and specificity of 96%. When compared to a composite reference of definite or probable TBM, the sensitivity was 24% and specificity was 95%. There were two false positive tests with TB-LAM (3+ grade). In-hospital mortality in CSF TB-LAM positive patients was 17% compared to 0% in those with definite TBM by Xpert MTB/Rif Ultra but negative LAM. Conclusions: Lumbar CSF TB-LAM has a poor performance in diagnosing TBM. Both urine TB-LAM and Xpert Ultra should be further investigated in the diagnosis of TBM.

Prospective Cohort Study on Performance of Cerebrospinal Fluid (CSF) Xpert MTB/RIF, CSF Lipoarabinomannan (LAM) Lateral Flow Assay (LFA), and Urine LAM LFA for Diagnosis of Tuberculous Meningitis in Zambia

Tuberculous meningitis (TBM) is a devastating infection of the central nervous system lacking an adequate point-of-care diagnostic test. We conducted a prospective cohort study of 550 Zambian adults with suspected TBM to determine the diagnostic accuracy of cerebrospinal fluid (CSF) Xpert MTB/RIF, CSF lipoarabinomannan (LAM), urine LAM, CSF total protein, and CSF glucose compared with the gold standard of CSF culture. We categorized patients with a positive CSF tuberculosis (TB) culture as definite TBM. We also assessed inpatient and 1-year mortality on definite TBM patients when CSF Xpert MTB/RIF results were available in real time to treating physicians relative to a historical comparison cohort in whom Xpert results were not available in real time. Of the 550 patients, 474 (86.2%) were HIV-infected and 105/550 (19.1%) had definite TBM based on a positive CSF culture. The sensitivity/specificity of the diagnostic tests were CSF Xpert MTB/RIF, 52.9%/94.2%; CSF LAM, 21.9%/94.2%; urine LAM, 24.1%/76.1%; and CSF glucose <40 mg/dl, and total protein, >100 mg/dl, 66.3%/90%. A model including CSF Xpert MTB/RIF, CSF LAM, CSF glucose, and CSF total protein demonstrated an area under the receiver operating curve of 0.90. The inpatient and 1-year mortality for definite TBM was 43% and 57%, respectively. There was low sensitivity for the diagnosis of TBM across all diagnostics tests. CSF Xpert MTB/RIF and CSF LAM are highly specific for the diagnosis of TBM. Despite the use of Xpert MTB/RIF for diagnostic purpose in real time, TBM was still associated with a high mortality in Zambian patients.

Neurological disorders in HIV in Africa: a review

BACKGROUND

Neurological disorders in HIV infection are a common cause of morbidity and mortality. The aim of this paper is to provide a narrative overview of up to date information concerning neurological disorders affecting HIV infected persons in Africa.

METHODS

Seminal research concerning neurological disorders among HIV-infected adults in sub-Saharan Africa from prior to 2000 was combined with an in-depth search of PubMed to identify literature published from 2000 to 2017. The following Mesh terms were used. "Nervous System Diseases" "HIV Infections" and "Africa South of the Sahara" and "Seizures" or "Spinal Cord Diseases" or "Peripheral Nervous System Diseases" or "AIDS Dementia Complex" or "Opportunistic Infections" or "Immune Reconstitution Inflammatory Syndrome" or "Stroke". Only those articles written in English were used. A total of 352 articles were identified, selected and reviewed and 180 were included in the study. These included case series, observational studies, interventional studies, guidelines and reviews with metanalyses. The author also included 15 publications on the subject covering the earlier phase of the HIV epidemic in Africa from 1987 to 1999 making a total of 195 references in the study. This was combined with extensive personal experience diagnosing and treating these neurological disorders.

RESULTS

Neurological disorders were common, typically occurring in WHO stages III/IV. These were in three main categories: those arising from opportunistic processes mostly infections, direct HIV infection and autoimmunity. The most common were those arising from direct HIV infection occurring in >50%. These included HIV-associated neurocognitive dysfunction (HAND), neuropathy and myelopathy. Opportunistic infections occurred in >20% and frequently had a 6-9-month mortality rate of 60-70%. The main causes were cryptococcus, tuberculosis, toxoplasmosis and acute bacterial meningitis. Concurrent systemic tuberculosis occurred in almost 50%.

CONCLUSION

Neurological disorders are common in HIV in Africa and the main CNS opportunistic infections result in high mortality rates. Strategies aimed at reducing their high burden, morbidity and mortality include early HIV diagnosis and anti-retroviral therapy (ART), screening and chemoprophylaxis of main opportunistic infections, improved clinical diagnosis and management and programme strengthening.

A Systematic Review and Meta-analysis of the Diagnostic Accuracy of Nucleic Acid Amplification Tests for Tuberculous Meningitis

The diagnosis of tuberculous meningitis (TBM) is difficult and poses a significant challenge to physicians worldwide. Recently, nucleic acid amplification (NAA) tests have shown promise for the diagnosis of TBM, although their performance has been variable. We undertook a systematic review and meta-analysis to evaluate the diagnostic accuracy of NAA tests with cerebrospinal fluid (CSF) samples against that of culture as the reference standard or a combined reference standard (CRS) for TBM. We searched the Embase, PubMed, Web of Science, and Cochrane Library databases for the relevant records. The QUADAS-2 tool was used to assess the quality of the studies. Diagnostic accuracy measures (i.e., sensitivity and specificity) were pooled with a random-effects model. All statistical analyses were performed with STATA (version 14 IC; Stata Corporation, College Station, TX, USA), Meta-DiSc (version 1.4 for Windows; Cochrane Colloquium, Barcelona, Spain), and RevMan (version 5.3; The Nordic Cochrane Centre, the Cochrane Collaboration, Copenhagen, Denmark) software. Sixty-three studies comprising 1,381 cases of confirmed TBM and 5,712 non-TBM controls were included in the final analysis. These 63 studies were divided into two groups comprising 71 data sets (43 in-house tests and 28 commercial tests) that used culture as the reference standard and 24 data sets (21 in-house tests and 3 commercial tests) that used a CRS. Studies which used a culture reference standard had better pooled summary estimates than studies which used CRS. The overall pooled estimates of sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) of the NAA tests against culture were 82% (95% confidence interval [CI], 75 to 87%), 99% (95% CI, 98 to 99%), 58.6 (95% CI, 35.3 to 97.3), and 0.19 (95% CI, 0.14 to 0.25), respectively. The pooled sensitivity, specificity, PLR, and NLR of NAA tests against CRS were 68% (95% CI, 41 to 87%), 98% (95% CI, 95 to 99%), 36.5 (95% CI, 15.6 to 85.3), and 0.32 (95% CI, 0.15 to 0.70), respectively. The analysis has demonstrated that the diagnostic accuracy of NAA tests is currently insufficient for them to replace culture as a lone diagnostic test. NAA tests may be used in combination with culture due to the advantage of time to result and in scenarios where culture tests are not feasible. Further work to improve NAA tests would benefit from the availability of standardized reference standards and improvements to the methodology.

Tuberculous meningitis

Tuberculosis remains a global health problem, with an estimated 10.4 million cases and 1.8 million deaths resulting from the disease in 2015. The most lethal and disabling form of tuberculosis is tuberculous meningitis (TBM), for which more than 100,000 new cases are estimated to occur per year. In patients who are co-infected with HIV-1, TBM has a mortality approaching 50%. Study of TBM pathogenesis is hampered by a lack of experimental models that recapitulate all the features of the human disease. Diagnosis of TBM is often delayed by the insensitive and lengthy culture technique required for disease confirmation. Antibiotic regimens for TBM are based on those used to treat pulmonary tuberculosis, which probably results in suboptimal drug levels in the cerebrospinal fluid, owing to poor blood-brain barrier penetrance. The role of adjunctive anti-inflammatory, host-directed therapies - including corticosteroids, aspirin and thalidomide - has not been extensively explored. To address this deficit, two expert meetings were held in 2009 and 2015 to share findings and define research priorities. This Review summarizes historical and current research into TBM and identifies important gaps in our knowledge. We will discuss advances in the understanding of inflammation in TBM and its potential modulation; vascular and hypoxia-mediated tissue injury; the role of intensified antibiotic treatment; and the importance of rapid and accurate diagnostics and supportive care in TBM.