The diagnostic accuracy of pericardial and urinary lipoarabinomannan (LAM) assays in patients with suspected tuberculous pericarditis

Diagnostic Performance of Unstimulated IFN-γ (IRISA-TB) for Pleural Tuberculosis: A Prospective Study in South Africa and India

Background

Tuberculous pleural effusion (TPE) is the most common form of extrapulmonary tuberculosis in many settings. The diagnostic performance of the frontline polymerase chain reaction-based GeneXpert MTB/RIF Ultra (Xpert Ultra) remains suboptimal (sensitivity of ∼30%), but data are limited. Improved diagnostic approaches are urgently needed to detect extrapulmonary tuberculosis (EPTB) in tuberculosis (TB)-endemic settings.

Methods

This multicenter, prospective cohort study evaluated the diagnostic performance of a rapid (same-day) interferon gamma rapid immunosuspension assay (IRISA-TB) in patients with presumed TPE from South Africa and India. Participants underwent pleural biopsy, and testing with other available same-day diagnostic assays (adenosine deaminase [ADA], Xpert Ultra, and IRISA-TB) was concurrently undertaken. The reference standard for TB was microbiological and/or histopathological confirmation using pleural fluid and/or pleural biopsy samples.

Results

A total of 217 participants with presumed TPE were recruited (106 from South Africa, 111 from India). The sensitivity of IRISA-TB (cut-point 20.5 pg/mL) was significantly better than that of Xpert Ultra (81.8% [70.4-90.2] vs 32.9% [22.1-45.1]; P < .001) and ADA at the 40 IU/mL cut-point used in India (81.8% [70.4-90.2] vs 53.8% [41.0-66.3]; P  = .002). Compared with ADA at the 30 IU/mL cut-point used in South Africa, IRISA-TB had a higher specificity (96.6% [90.3-99.3] vs 87.1% [78.6-93.2]) and a higher positive predictive value (94.7% [85.5-97.3] vs 81.8% [72.4-88.5]). The negative predictive value (NPV; rule-out value) of IRISA-TB was significantly better than that of Xpert Ultra (87.5% [83.2-93.0] vs 64.9% [61.1-68.6]; P < .001) and ADA at the 40 IU/mL cut-point (87.5% [83.2-93.0] vs 74.1% [68.7-79.0]; P < .001).

Conclusions

IRISA-TB demonstrated markedly better sensitivity and NPV than Xpert Ultra and excellent specificity for the diagnosis of TPE. These data have implications for clinical practice in TB-endemic settings.

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.

Urinary lipoarabinomannan in individuals with sputum-negative pulmonary tuberculosis

BACKGROUND OBJECTIVES

Tuberculosis (TB) is a major global cause of ill health. Sputum microscopy for confirmation of presumptive pulmonary TB (PTB) has a reportedly low sensitivity of 22-43 per cent for single smear and up to 60 per cent under optimal conditions. National TB Elimination Programme in India recommends the use of cartridge-based nucleic acid amplification test (CBNAAT) and culture for microbiological confirmation in presumptive PTB individuals with sputum smear negative test. The use of lateral flow urine lipoarabinomannan (LF-LAM) is usually recommended for the diagnosis of TB in HIV-positive individuals with low CD4 counts or those who are seriously ill. The objective of this study was to detect urinary LAM using cage nanotechnology that does not require a physiologic or immunologic consequence of HIV infection for LAM quantification in human urine in 50 HIV-seronegative sputum smear-negative PTB individuals.

METHODS

To study the diagnostic value of urinary LAM in sputum smear negative PTB individuals, a cage based nanotechnology ELISA technique was used for urinary LAM in three different groups of participants. Fifty smears negative PTB clinically diagnosed, 15 smear positive PTB and 15 post TB sequel individuals. Sputum was tested by smear, CBNAAT, and culture along with urine LAM before treatment. The results were interpreted by ROC curve in comparison to the standard tests like CBNAAT and culture.

RESULTS

The mean urinary LAM value was 0.84 ng/ml in 37 culture-positive [Mycobacterium tuberculosis (M.tb)] and 0.49 ng/ml in 13 culture-negative (M.tb) smear-negative individuals with PTB, respectively. In 47 smear-negative PTB cases with microbiologically confirmed TB by CBNAAT, the mean urinary LAM was 0.76 ng/ml. The mean urinary LAM in post-TB sequel individuals was 0.47 ng/ml. As per the receiver operating characteristic curve, cut-off value of urinary LAM in individuals with smear-negative PTB microbiologically confirmed by: (i) CBNAAT was 0.695 ng/ml and (ii) culture was 0.615 ng/ml.

INTERPRETATION CONCLUSIONS

The findings of this study suggest that individuals with smear-negative PTB and a urinary LAM value of >0.615 ng/ml were most likely to have microbiological confirmed TB while those with a LAM value <0.615 ng/ml >0.478 ng/ml are less likely and those with a value <0.478 ng/ml are unlikely to have microbiological confirmed TB.

The Efficiency of TB LAM Antigen Test to Xpert MTB/RIF Ultra Test for the Diagnosis of Tuberculous Pericarditis Using Pericardial Fluid Samples

Medical considerations for early diagnosis of tuberculous pericarditis (TBP) include Xpert MTB/RIF Ultra and TB lipoarabinomannan (LAM) antigen (Ag) tests, with immunological status influencing the performance of the latter. An evaluation of the efficiency of Xpert MTB/RIF Ultra and TB LAM Ag in detecting TBP was conducted using pericardial fluid samples from 46 patients with suspected TBP. Fifteen patients (34.1%) were diagnosed with TBP according to culture results. TB LAM Ag's sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were 33.3%, 100%, 100%, 74.4%, 0, and 0.67, respectively. The sensitivity, specificity, PLR, NLR, PPV, and NPV of Xpert MTB/RIF Ultra were 80%, 93.1%, 11.6, 0.21, 85.7%, and 90%, respectively. There was an association observed between a positive TB LAM Ag test and HIV status. When compared to the Xpert MTB/RIF Ultra test, TB LAM Ag has lower accuracy for the detection of microbiologically proven tuberculous pericarditis, yet its usage in HIV-positive populations may be worth exploring. The TB LAM Ag assay is not the best first-line test for the diagnosis of tuberculous pericarditis, and it should be used in conjunction with other diagnostic tests.

Cardiovascular Involvement in Tuberculosis: From Pathophysiology to Diagnosis and Complications-A Narrative Review

Although primarily a lung disease, extra-pulmonary tuberculosis (TB) can affect any organ or system. Of these, cardiovascular complications associated with disease or drug toxicity significantly worsen the prognosis. Approximately 60% of patients with TB have a cardiovascular disease, the most common associated pathological entities being pericarditis, myocarditis, and coronary artery disease. We searched the electronic databases PubMed, MEDLINE, and EMBASE for studies that evaluated the impact of TB on the cardiovascular system, from pathophysiological mechanisms to clinical and paraclinical diagnosis of cardiovascular involvement as well as the management of cardiotoxicity associated with antituberculosis medication. The occurrence of pericarditis in all its forms and the possibility of developing constrictive pericarditis, the association of concomitant myocarditis with severe systolic dysfunction and complication with acute heart failure phenomena, and the long-term development of aortic aneurysms with risk of complications, as well as drug-induced toxicity, pose complex additional problems in the management of patients with TB. In the era of multidisciplinarity and polymedication, evidence-based medicine provides various tools that facilitate an integrative management that allows early diagnosis and treatment of cardiac pathologies associated with TB.

Subacute Cardiac Tamponade Due to Tuberculous Pericarditis Diagnosed by Urine Lipoarabinomannan Assay in a Immunocompetent Patient in Oyam District, Uganda: A Case Report

BACKGROUND

Uganda ranks among the countries with the highest burden of TB the world and tuberculous pericarditis (TBP) affects up to 2% of people diagnosed with pulmonary tuberculosis worldwide. In Africa, it represents the most common cause of pericardial disease. Here, we present the case of a 21-year-old male patient who was diagnosed of cardiac tamponade due to tuberculous pericarditis with a positive urine LF-LAM.

CASE REPORT

We report a case of a 21-year-old male living in Oyam district, Uganda, who presented to the emergency department with difficulty in breathing, easy fatigability, general body weakness, and abdominal pain. A chest X-ray showed the presence of right pleural effusion and massive cardiomegaly. Thus, percutaneous pericardiocentesis was performed immediately and pericardial fluid resulted negative both for gram staining and real-time PCR test Xpert MTB/RIF. The following day's urine LF-LAM test resulted positive, and antitubercular therapy started with gradual improvement. During the follow-up visits, the patient remained asymptomatic, reporting good compliance to the antitubercular therapy.

CONCLUSION

Our case highlights the potential usefulness of a LF-LAM-based diagnostic approach, suggesting that, in low-resource settings, this test might be used as part of routine diagnostic workup in patients with pericardial disease or suspected extra-pulmonary tuberculosis.

Comparison of the frequency and phenotypic profile of Mycobacterium tuberculosis-specific CD4 T cells between the site of disease and blood in pericardial tuberculosis

Studies of the immune response at the site of disease in extra-pulmonary tuberculosis (EPTB) disease are scarce. In this study, we compared the cellular profile of Mycobacterium tuberculosis (Mtb)-specific T cells in pericardial fluid and peripheral blood in patients with pericardial TB (PCTB). Whole blood and pericardial fluid (PCF) samples were collected at the time of diagnostic sampling, with repeat blood sampling after completion of anti-tubercular treatment (ATT) in 16 PCTB patients, most of them being HIV-1 infected (n=14). These samples were stimulated ex vivo and the phenotypic and functional cellular profile of PCF and blood was assessed by flow cytometry. We found that lymphocytes were the predominant cell type in PCF in PCTB, with a preferential influx of CD4 T cells. The frequencies of TNF-α producing Mtb-specific granulocytes and Mtb-specific CD4 T cells were significantly higher in PCF compared to blood. Mtb-specific CD4 T cells in PCF exhibited a distinct phenotype compared to those in blood, with greater GrB expression and lower CD27 and KLRG1 expression. We observed no difference in the production IFNγ, TNF or IL-2 by Mtb-specific CD4 T cells between the two compartments, but MIP-1β production was lower in the PCF T cells. Bacterial loads were not associated with alterations in the phenotype or function of Mtb-specific CD4 T cells. Upon ATT completion, HLA-DR, Ki-67 and GrB expression was significantly decreased, and relative IL-2 production was increased in peripheral Mtb-specific CD4 T cells. Overall, using an ex vivo assay to compare the immune response towards Mtb in PCF and in blood, we identified significant difference in the phenotypic profile of Mtb-specific CD4 T response between these two compartments. Moreover, we show that the activation profile of peripheral Mtb-specific CD4 T cells could be used to monitor treatment response in PCTB.

Diagnostic value of Lipoarabinomannan antigen for detecting Mycobacterium tuberculosis in adults and children with or without HIV infection

Objectives

Even today, tuberculosis (TB) remains a leading public health problem; yet, the current diagnostic methods still have a few shortcomings. Lipoarabinomannan (LAM) provides an opportunity for TB diagnosis, and urine LAM detection seems to have a promising and widely applicable prospect.

Design or methods

Four databases were systematically searched for eligible studies, and the quality of the studies was evaluated using the quality assessment of diagnostic accuracy studies‐2 (QUADAS‐2). Graphs and tables were created to show sensitivity, specificity, likelihood ratios, diagnostic odds ratio (DOR), the area under the curve (AUC), and so on.

Results

Based on the included 67 studies, the pooled sensitivity of urine LAM was 48% and specificity was 89%. In the subgroup analyses, the FujiLAM test had higher sensitivity (69%) and specificity (92%). Furthermore, among patients infected with human immunodeficiency virus (HIV), 50% of TB patients were diagnosed using a urine LAM test. Besides, the CD4+ cell count was inversely proportional to the sensitivity.

Conclusions

Urine LAM is a promising diagnostic test for TB, particularly using the FujiLAM in HIV‐infected adults whose CD4+ cell count is ≤100 per μl. Besides, the urine LAM test shows various sensitivities and specificities in different subgroups in terms of age, HIV infection status, CD4+ cell count, and testing method.

Tuberculous pericardial disease: a focused update on diagnosis, therapy and prevention of complications

Tuberculous pericarditis (TBP) is the most important manifestation of tuberculous heart disease and is still associated with a significant morbidity and mortality in TB endemic areas. The high prevalence of the disorder over the last 3 decades has been fueled by the human immunodeficiency virus/AIDS (HIV/AIDS) pandemic in these areas. The objective of this review is to provide a focused update on developments in the diagnosis and therapy of this condition, prevention of its complications, as well as future novel therapies. The definitive diagnosis of a tuberculous etiology in patients with suspected TBP continues to pose a challenge for clinicians. Clinical prediction scores, although never formally validated have been used with some success. However, they may be prone to both over and underdiagnosis due to lack of pericardial fluid analysis. Recent studies evaluating Xpert MTB/RIF, suggest that this advanced polymerase chain reaction (PCR) based technology does not provide increased accuracy compared to earlier iterations. However a combined two test approach starting with Xpert MTB/RIF followed by either adenosine deaminase (ADA) or interferon gamma (IFN-γ) may provide for significantly enhanced specificity and sensitivity cost permitting. Pericardiocentesis remains the gold standard for managing the compressive pericardial fluid and its adverse hemodynamic sequelae. A four drug anti-TB drug regimen at standard doses and duration is recommended. However recent evidence suggests that these drugs penetrate the pericardium very poorly potentially explaining the high mortality observed particularly in those who are culture positive with a high bacillary load. Constrictive pericarditis is the main long-term complication of TBP and is still a significant cause of heart failure in Sub-Saharan Africa. This is important because access to definitive surgical therapy where TBP is prevalent continues to be low, highlighting the need to develop strategies or interventions to prevent fibrosis and constriction. Recent detailed advanced studies of pericardial fluid in TBP have revealed a strong profibrotic transcriptomic profile, with high amounts of pro-inflammatory cytokines and low levels of the anti-fibrotic tetrapeptide N-Acetyl-Seryl-Aspartyl-Lysyl-Proline (Ac-SDKP). These new insights may explain in part the high propensity to fibrosis associated with the condition and offer hope for the future use of targeted therapy to interrupt pathways and mediators of tissue damage and subsequent maladaptive healing and fibrosis. The value of effective pericardiocentesis in reducing these pro-inflammatory and pro-fibrotic cytokines and peptides in an attempt to prevent pericardial constriction has yet to be established but has generated hypotheses for ongoing and future research.

Lateral flow urine lipoarabinomannan assay for detecting active tuberculosis in people living with HIV

BACKGROUND

The lateral flow urine lipoarabinomannan (LF-LAM) assay Alere Determine™ TB LAM Ag is recommended by the World Health Organization (WHO) to help detect active tuberculosis in HIV-positive people with severe HIV disease. This review update asks the question, "does new evidence justify the use of LF-LAM in a broader group of people?", and is part of the WHO process for updating guidance on the use of LF-LAM.

OBJECTIVES

To assess the accuracy of LF-LAM for the diagnosis of active tuberculosis among HIV-positive adults with signs and symptoms of tuberculosis (symptomatic participants) and among HIV-positive adults irrespective of signs and symptoms of tuberculosis (unselected participants not assessed for tuberculosis signs and symptoms).The proposed role for LF-LAM is as an add on to clinical judgement and with other tests to assist in diagnosing tuberculosis.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; MEDLINE, Embase, Science Citation Index, Web of Science, Latin American Caribbean Health Sciences Literature, Scopus, the WHO International Clinical Trials Registry Platform, the International Standard Randomized Controlled Trial Number Registry, and ProQuest, without language restriction to 11 May 2018.

SELECTION CRITERIA

Randomized trials, cross-sectional, and observational cohort studies that evaluated LF-LAM for active tuberculosis (pulmonary and extrapulmonary) in HIV-positive adults. We included studies that used the manufacturer's recommended threshold for test positivity, either the updated reference card with four bands (grade 1 of 4) or the corresponding prior reference card grade with five bands (grade 2 of 5). The reference standard was culture or nucleic acid amplification test from any body site (microbiological). We considered a higher quality reference standard to be one in which two or more specimen types were evaluated for tuberculosis diagnosis and a lower quality reference standard to be one in which only one specimen type was evaluated.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data using a standardized form and REDCap electronic data capture tools. We appraised the quality of studies using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool and performed meta-analyses to estimate pooled sensitivity and specificity using a bivariate random-effects model and a Bayesian approach. We analyzed studies enrolling strictly symptomatic participants separately from those enrolling unselected participants. We investigated pre-defined sources of heterogeneity including the influence of CD4 count and clinical setting on the accuracy estimates. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 15 unique studies (nine new studies and six studies from the original review that met the inclusion criteria): eight studies among symptomatic adults and seven studies among unselected adults. All studies were conducted in low- or middle-income countries. Risk of bias was high in the patient selection and reference standard domains, mainly because studies excluded participants unable to produce sputum and used a lower quality reference standard.Participants with tuberculosis symptomsLF-LAM pooled sensitivity (95% credible interval (CrI) ) was 42% (31% to 55%) (moderate-certainty evidence) and pooled specificity was 91% (85% to 95%) (very low-certainty evidence), (8 studies, 3449 participants, 37% with tuberculosis).For a population of 1000 people where 300 have microbiologically-confirmed tuberculosis, the utilization of LF-LAM would result in: 189 to be LF-LAM positive: of these, 63 (33%) would not have tuberculosis (false-positives); and 811 to be LF-LAM negative: of these, 174 (21%) would have tuberculosis (false-negatives).By clinical setting, pooled sensitivity was 52% (40% to 64%) among inpatients versus 29% (17% to 47%) among outpatients; and pooled specificity was 87% (78% to 93%) among inpatients versus 96% (91% to 99%) among outpatients. Stratified by CD4 cell count, pooled sensitivity increased, and specificity decreased with lower CD4 cell count.Unselected participants not assessed for signs and symptoms of tuberculosisLF-LAM pooled sensitivity was 35% (22% to 50%), (moderate-certainty evidence) and pooled specificity was 95% (89% to 96%), (low-certainty evidence), (7 studies, 3365 participants, 13% with tuberculosis).For a population of 1000 people where 100 have microbiologically-confirmed tuberculosis, the utilization of LF-LAM would result in: 80 to be LF-LAM positive: of these, 45 (56%) would not have tuberculosis (false-positives); and 920 to be LF-LAM negative: of these, 65 (7%) would have tuberculosis (false-negatives).By clinical setting, pooled sensitivity was 62% (41% to 83%) among inpatients versus 31% (18% to 47%) among outpatients; pooled specificity was 84% (48% to 96%) among inpatients versus 95% (87% to 99%) among outpatients. Stratified by CD4 cell count, pooled sensitivity increased, and specificity decreased with lower CD4 cell count.

AUTHORS' CONCLUSIONS

We found that LF-LAM has a sensitivity of 42% to diagnose tuberculosis in HIV-positive individuals with tuberculosis symptoms and 35% in HIV-positive individuals not assessed for tuberculosis symptoms, consistent with findings reported previously. Regardless of how people are enrolled, sensitivity is higher in inpatients and those with lower CD4 cell, but a concomitant lower specificity. As a simple point-of-care test that does not depend upon sputum evaluation, LF-LAM may assist with the diagnosis of tuberculosis, particularly when a sputum specimen cannot be produced.

The Mycobacterial HBHA Protein: A Promising Biomarker for Tuberculosis

A major goal in tuberculosis (TB) research is the identification, among the subjects infected with Mycobacterium tuberculosis (Mtb), of those with active TB, or at higher risk of developing active disease, from the latently infected subjects. The classical heterogeneity of Mtb infection and TB disease is a major obstacle toward the identification of reliable biomarkers that can stratify Mtb infected subjects based on disease risk. The heparin-binding haemagglutinin (HBHA) is a mycobacterial surface antigen that is implicated in tuberculosis (TB) pathogenesis. The host immune response against HBHA varies depending on the TB status and several studies are supporting the role of HBHA as a useful biomarker of TB.

Mycobacterium tuberculosis Mannose-Capped Lipoarabinomannan Induces IL-10-Producing B Cells and Hinders CD4+Th1 Immunity

The importance of Th1/interferon (IFN)-γ-mediated responses in mycobacterial infection has been well established. However, little is known about B cell-mediated immunity during Mycobacterium tuberculosis (Mtb) infection. Interleukin (IL)-10-producing B cells (B10 cells), a subset of B regulatory cells (Bregs), are implicated in modulating the immune response. Herein, we found that B10 cells were significantly increased in patients with tuberculosis. Furthermore, mannose-capped lipoarabinomannan (ManLAM), a major surface lipoglycan component from Mtb, induced a significant increase in B10 cells, which enriched in CD5⁺ B1a B cells. ManLAM induced IL-10 production mainly by activating MyD88/PI3K/AKT/Ap-1 and K63-linked ubiquitination of NF-κB essential modulator/nuclear factor kappa-light-chain-enhancer of activated B cells signaling pathways in B cells via Toll-like receptor 2. IL-10 production by ManLAM-treated B cells further inhibited CD4⁺ Th1 polarization, leading to increased susceptibility to mycobacterial infection compared with ManLAM-treated IL-10^−/− B group. Thus, we report a new immunoregulation mechanism in which Mtb ManLAM-induced B10 cells negatively regulate host anti-TB cellular immunity.

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Mtb mannose-capped lipoarabinomannan (ManLAM) induces IL-10 production in B cells

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ManLAM-induced B10 cells enrich in CD5⁺ B1a B cells

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ManLAM binding with TLR2 triggers MyD88 signaling pathways of B cells

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ManLAM-induced B10 cells hinder CD4⁺Th1 immunity during Mtb infection in mice

Urine lipoarabinomannan glycan in HIV-negative patients with pulmonary tuberculosis correlates with disease severity

An accurate urine test for pulmonary tuberculosis (TB), affecting 9.6 million patients worldwide, is critically needed for surveillance and treatment management. Past attempts failed to reliably detect the mycobacterial glycan antigen lipoarabinomannan (LAM), a marker of active TB, in HIV-negative, pulmonary TB–infected patients’ urine (85% of 9.6 million patients). We apply a copper complex dye within a hydrogel nanocage that captures LAM with very high affinity, displacing interfering urine proteins. The technology was applied to study pretreatment urine from 48 Peruvian patients, all negative for HIV, with microbiologically confirmed active pulmonary TB. LAM was quantitatively measured in the urine with a sensitivity of >95%and a specificity of >80% (n = 101) in a concentration range of 14 to 2000 picograms per milliliter, as compared to non-TB, healthy and diseased, age-matched controls (evaluated by receiver operating characteristic analysis; area under the curve, 0.95; 95% confidence interval, 0.9005 to 0.9957). Urinary LAM was elevated in patients with a higher mycobacterial burden (n = 42), a higher proportion of weight loss (n = 37), or cough (n = 50). The technology can be configured in a variety of formats to detect a panel of previously undetectable very-low-abundance TB urinary analytes. Eight of nine patients who were smear-negative and culture-positive for TB tested positive for urinary LAM. This technology has broad implications for pulmonary TB screening, transmission control, and treatment management for HIV-negative patients.

Comparison between the diagnostic validities of Xpert MTB/RIF and interferon-γ release assays for tuberculous pericarditis using pericardial tissue

BACKGROUND

This study aimed to assess the diagnostic performance of Xpert MTB/RIF for tuberculous pericarditis (TBP) using pericardial tissues.

METHODS

The study involved 30 patients admitted with suspected TBP from January-December 2016; three patients were later excluded. The interferon-γ release assay (T-SPOT.TB) and the Xpert MTB/RIF test were performed using peripheral blood and pericardial tissues, respectively. TBP was confirmed using pericardial histopathology and a composite reference standard (CRS). We analyzed the sensitivity, specificity, predictive value (PV), likelihood ratio (LR), and area under curve (AUC) of both assays.

RESULTS

Fourteen patients were confirmed as TBP, 10 as non-TBP, and 3 as probable TBP. The sensitivity, specificity, positive PV (PPV), negative PV (NPV), PLR, NLR, and AUC (95% confidence interval [CI]) of the Xpert MTB/RIF assay were 78.6% (49.2-95.3%) and 70.6% (44.0-89.7%); 92.3% (64.0-99.8%) and 100% (69.2-100%); 91.7% (61.5-99.8%) and 100% (73.5-100%); 80.0% (51.9-95.7%) and 66.7% (38.4-88.2%); 10.21 (1.52-68.49) and the PLR value was undefined with CRS as the reference; 0.23 (0.08-0.64) and 0.29(0.14-0.61); and 0.854 (0.666-0.959) and 0.853 (0.664-0.959), against histopathology and CRS, respectively. The sensitivity, specificity, PPV, NPV, PLR, NLR, and AUC values (95% CI) of T-SPOT.TB were 92.9% (66.1-99.8%) and 94.1% (71.3-99.9%); 15.4% (1.9-45.5%) and 20.0% (2.5-55.6%); 54.2% (32.8-74.5%) and 66.7% (44.7-84.4%); 66.7% (9.4-99.2%) and 66.7% (9.4-99.2%); 1.10 (0.83-1.44) and 1.18 (0.84-1.6); 0.46 (0.05-4.53) and 0.29 (0.03-2.85); and 0.541(0.340-0.733) and 0.571(0.367-0.758), against histopathology and CRS, respectively. The differences in sensitivity, PPV, and AUC of Xpert MTB/RIF and T-SPOT.TB were not statistically significant (P > 0.05), compared to those of histopathology and CRS. However, the differences in specificity and NPV of the two assays were significant (P < 0.05), compared to those of histopathology and CRS.

CONCLUSIONS

Xpert MTB/RIF test is a valid diagnostic technique for TBP with higher sensitivity and specificity than T-SPOT.TB.

GeneXpert MTB/RIF assay in the diagnosis of urinary tuberculosis from urine specimens

Conventional bacteriological methods are not generally helpful in diagnosing urinary tuberculosis (UTB). GeneXpert is endorsed for the detection of pulmonary tuberculosis, whereas the data on its utility for urine specimens is limited. In this study, we aimed to evaluate its performance on urine specimens in a country with high TB incidence. A total of 163 suspected UTB patients were consecutively enrolled in the analysis, including 37 (22.7%) culture-positive and 44 (27.0%) clinically diagnosed UTB cases. Compared with conventional culture, the sensitivity of GeneXpert (94.6%) was significantly higher than that of smear microscopy (40.5%, P < 0.001). When setting clinical diagnosis as gold standard, 51 out of 81 clinically diagnosed UTB cases were detected by GeneXpert, demonstrating a sensitivity of 63.0%, which was significantly higher than that of smear microscopy (18.5%, P < 0.001) and culture (45.7%, P = 0.027), respectively. In addition, the proportion of UTB cases in the migrant population was significantly higher than that in the resident population (P = 0.019). To conclude, our data demonstrate that GeneXpert outperforms AFB smear and culture for the detection of MTB in urine samples, which provides an alternative for the diagnosis of UTB. The migrant population and previously diagnosed TB cases are high risk factors for developing UTB cases.