Diagnostic accuracy of a urine lipoarabinomannan enzyme-linked immunosorbent assay for screening ambulatory HIV-infected persons for tuberculosis

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.

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.

Algorithm-guided empirical tuberculosis treatment for people with advanced HIV (TB Fast Track): an open-label, cluster-randomised trial

BACKGROUND

Tuberculosis, which is often undiagnosed, is the major cause of death among HIV-positive people. We aimed to test whether the use of a clinical algorithm enabling the initiation of empirical tuberculosis treatment by nurses in primary health-care clinics would reduce mortality compared with standard of care for adults with advanced HIV disease.

METHODS

In this open-label cluster-randomised controlled trial, we recruited individuals from 24 primary health-care clinics in South Africa. The clinics were randomly assigned (1:1) to either deliver an intervention or routine care (control) using computer-generated random numbers. Eligible participants were HIV-positive adults (aged ≥18 years) with CD4 counts of 150 cells per μL or less, who had not had antiretroviral therapy (ART) in the past 6 months or tuberculosis treatment in the past 3 months, and did not require urgent hospital referral. In intervention clinics, study nurses assessed participants on the basis of tuberculosis symptoms, body-mass index, point-of-care haemoglobin concentrations, and urine lipoarabinomannan assay results. Participants classified by a study algorithm as having high probability of tuberculosis (positive urine lipoarabinomannan assay, body-mass index <18·5 kg/m², or haemoglobin concentration <100 g/L) were recommended to start tuberculosis treatment immediately followed by ART 2 weeks later; participants classified as medium probability (tuberculosis symptoms, no high probability criteria) were recommended to have symptom-guided investigation; and participants classified as low probability (no tuberculosis symptoms or high probability criteria) were recommended to start ART immediately. In standard-of-care clinics, participants received treatment in accordance with South African guidelines. Investigators and participants were aware of treatment allocation. The primary outcome was all-cause mortality at 6 months, assessed in the intention-to-treat population. Safety was also analysed in the intention-to treat population. This trial is registered with the ISRCTN registry, ISRCTN35344604, and the South African National Clinical Trials Register, DOH-27-0812-3902.

FINDINGS

Between Dec 19, 2012, and Dec 18, 2014, 3091 individuals were screened for eligibility, of whom 3053 were recruited, and 3022 (1507 participants in the intervention group and 1515 participants in the control group) were analysed for the primary outcome. 930 (61·7%) of 1507 participants in the intervention group versus 172 (11·4%) of 1515 participants in the control group had started tuberculosis treatment by 2 months. At 6 months, the mortality rate was 19·0 deaths per 100 person-years for the intervention group versus 21·6 deaths per 100 person-years in the control group (unadjusted hazard ratio [HR] 0·92, 95% CI 0·67-1·26, p=0·58; adjusted HR 0·87, 0·61-1·24, p=0·41). 28 (1·9%) of 1507 participants in the intervention group and ten (0·7%) of 1515 participants in the control group reported serious or severe adverse events. Grade 3 or 4 nausea and vomiting was the most common adverse event (ten participants in the intervention group and four participants in the control group). Among participants with adverse events, eight participants (six participants in the intervention group and two participants in the control group) died; none of the six deaths in the intervention group were attributed to the study intervention.

INTERPRETATION

Our intervention substantially increased coverage of tuberculosis treatment in this high-risk population, but did not reduce mortality.

FUNDING

Joint Global Health Trials (Medical Research Council, Department for International Development, Wellcome Trust).

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.

Urine lipoarabinomannan (LAM) and antimicrobial usage in seriously-ill HIV-infected patients with sputum smear-negative pulmonary tuberculosis

Background

Based on current WHO guidelines, hospitalized tuberculosis (TB) and HIV co-infected patients with CD4 count <100 cells/mm³ who are urine lipoarabinomannan (LAM) positive should be initiated on TB treatment. This recommendation is conditional, and data are limited in sputum smear-negative patients from TB endemic countries where the LAM test is largely inaccessible. Other potential benefits of LAM, including reduction in antibiotic usage have, hitherto, not been explored.

Methods

We consecutively enrolled newly-admitted seriously-ill HIV-infected patients (n=187) with suspected TB from three hospitals in KwaZulu-Natal, South Africa. All patients were empirically treated for TB as per the WHO 2007 smear-negative TB algorithm (patients untreated for TB were not recruited). Bio-banked urine, donated prior to anti-TB treatment, was tested for TB-infection using a commercially available LAM-ELISA test. TB sputum and blood cultures were performed.

Results

Data from 156 patients containing CD4 count, urine-LAM, sputum and blood culture results were analysed. Mean age was 37 years, median CD4-count was 75 cells/mm³ [interquartile range (IQR), 34-169 cells/mm³], 54/156 (34.6%) were sputum culture-positive, 12/54 (22.2%) blood-culture positive, and 53/156 (34.0%) LAM-positive. Thus, LAM sensitivity was 55.6% (30/54). The study design did not allow for calculation of specificity. Urine-LAM positivity was associated with low CD4 count (P=0.002). Ninety-point-six percent (48/53) of LAM-positive patients received antibiotics [15/48 (31.3%), 23/48 (47.9%) and 10/48 (20.8%) received one, two or three different antibiotics respectively], while the duration of antibiotic therapy was more than 5 days in 26 of 46 (56.5%) patients.

Conclusions

Urine LAM testing in sputum smear-negative severely-ill hospitalized patients with TB-HIV co-infection and advanced immunosuppression, offered an immediate rule-in diagnosis in one-third of empirically treated patients. Moreover, LAM, by providing a rapid alternative diagnosis, could potentially reduce antibiotic overusage in such patients thereby reducing health-care costs and facilitating antibiotic stewardship.

Biomarkers for tuberculosis: the case for lipoarabinomannan

Tuberculosis (TB) is considered the most onerous of infectious diseases according to recent reports from the World Health Organization. Available tests for TB diagnosis present severe limitations, and a reliable point-of-care (POC) diagnostic test does not exist. Neither is there a test to discern between the different stages of TB, and in particular to predict which patients with Mycobacterium tuberculosis infection and no clinical signs are more at risk of advancing to overt disease. We here review the usefulness of mycobacterial lipoarabinomannan (LAM) as a diagnostic marker for active and latent TB and, also, aspects of the immune response to LAM relevant to such tests. There is a high potential for urinary LAM-based POC tests for the diagnosis of active TB. Some technical challenges to optimised sensitivity of the test will be detailed. A method to quantify LAM in urine or serum should be further explored as a test of treatment effect. Recent data on the immune response to LAM suggest that markers for host response to LAM should be investigated for a prognostic test to recognise individuals at the greatest risk of disease activation.

There is a high potential for a urinary LAM-based point-of-care test to diagnose TB. Markers for host response to LAM should be explored to identify those at highest risk of developing active TB.http://ow.ly/FyCs30n4uFE

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.

Lateral flow urine lipoarabinomannan assay for detecting active tuberculosis in HIV-positive adults

BACKGROUND

Rapid detection of tuberculosis (TB) among people living with human immunodeficiency virus (HIV) is a global health priority. HIV-associated TB may have different clinical presentations and is challenging to diagnose. Conventional sputum tests have reduced sensitivity in HIV-positive individuals, who have higher rates of extrapulmonary TB compared with HIV-negative individuals. The lateral flow urine lipoarabinomannan assay (LF-LAM) is a new, commercially available point-of-care test that detects lipoarabinomannan (LAM), a lipopolysaccharide present in mycobacterial cell walls, in people with active TB disease.

OBJECTIVES

To assess the accuracy of LF-LAM for the diagnosis of active TB disease in HIV-positive adults who have signs and symptoms suggestive of TB (TB diagnosis).To assess the accuracy of LF-LAM as a screening test for active TB disease in HIV-positive adults irrespective of signs and symptoms suggestive of TB (TB screening).

SEARCH METHODS

We searched the following databases without language restriction on 5 February 2015: the Cochrane Infectious Diseases Group Specialized Register; MEDLINE (PubMed,1966); EMBASE (OVID, from 1980); Science Citation Index Expanded (SCI-EXPANDED, from 1900), Conference Proceedings Citation Index-Science (CPCI-S, from 1900), and BIOSIS Previews (from 1926) (all three using the Web of Science platform; MEDION; LILACS (BIREME, from 1982); SCOPUS (from 1995); the metaRegister of Controlled Trials (mRCT); the search portal of the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP); and ProQuest Dissertations & Theses A&l (from 1861).

SELECTION CRITERIA

Eligible study types included randomized controlled trials, cross-sectional studies, and cohort studies that determined LF-LAM accuracy for TB against a microbiological reference standard (culture or nucleic acid amplification test from any body site). A higher quality reference standard was one in which two or more specimen types were evaluated for TB, and a lower quality reference standard was one in which only one specimen type was evaluated for TB. Participants were HIV-positive people aged 15 years and older.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from each included study using a standardized form. We appraised the quality of studies using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. We evaluated the test at two different cut-offs: (grade 1 or 2, based on the reference card scale of five intensity bands). Most analyses used grade 2, the manufacturer's currently recommended cut-off for positivity. We carried out meta-analyses to estimate pooled sensitivity and specificity using a bivariate random-effects model and estimated the models using a Bayesian approach. We determined accuracy of LF-LAM combined with sputum microscopy or Xpert® MTB/RIF. In addition, we explored the influence of CD4 count on the accuracy estimates. We assessed the quality of the evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included 12 studies: six studies evaluated LF-LAM for TB diagnosis and six studies evaluated the test for TB screening. All studies were cross-sectional or cohort studies. Studies for TB diagnosis were largely conducted among inpatients (median CD4 range 71 to 210 cells per µL) and studies for TB screening were largely conducted among outpatients (median CD4 range 127 to 437 cells per µL). All studies were conducted in low- or middle-income countries. Only two studies for TB diagnosis (33%) and one study for TB screening (17%) used a higher quality reference standard.LF-LAM for TB diagnosis (grade 2 cut-off): meta-analyses showed median pooled sensitivity and specificity (95% credible interval (CrI)) of 45% (29% to 63%) and 92% (80% to 97%), (five studies, 2313 participants, 35% with TB, low quality evidence). The pooled sensitivity of a combination of LF-LAM and sputum microscopy (either test positive) was 59% (47% to 70%), which represented a 19% (4% to 36%) increase over sputum microscopy alone, while the pooled specificity was 92% (73% to 97%), which represented a 6% (1% to 24%) decrease from sputum microscopy alone (four studies, 1876 participants, 38% with TB). The pooled sensitivity of a combination of LF-LAM and sputum Xpert® MTB/RIF (either test positive) was 75% (61% to 87%) and represented a 13% (1% to 37%) increase over Xpert® MTB/RIF alone. The pooled specificity was 93% (81% to 97%) and represented a 4% (1% to 16%) decrease from Xpert® MTB/RIF alone (three studies, 909 participants, 36% with TB). Pooled sensitivity and specificity of LF-LAM were 56% (41% to 70%) and 90% (81% to 95%) in participants with a CD4 count of less than or equal to 100 cells per µL (five studies, 859 participants, 47% with TB) versus 26% (16% to 46%) and 92% (78% to 97%) in participants with a CD4 count greater than 100 cells per µL (five studies, 1410 participants, 30% with TB).LF-LAM for TB screening (grade 2 cut-off): for individual studies, sensitivity estimates (95% CrI) were 44% (30% to 58%), 28% (16% to 42%), and 0% (0% to 71%) and corresponding specificity estimates were 95% (92% to 97%), 94% (90% to 97%), and 95% (92% to 97%) (three studies, 1055 participants, 11% with TB, very low quality evidence). There were limited data for additional analyses.The main limitations of the review were the use of a lower quality reference standard in most included studies, and the small number of studies and participants included in the analyses. The results should, therefore, be interpreted with caution.

AUTHORS' CONCLUSIONS

We found that LF-LAM has low sensitivity to detect TB in adults living with HIV whether the test is used for diagnosis or screening. For TB diagnosis, the combination of LF-LAM with sputum microscopy suggests an increase in sensitivity for TB compared to either test alone, but with a decrease in specificity. In HIV-positive individuals with low CD4 counts who are seriously ill, LF-LAM may help with the diagnosis of TB.

Biomarkers for Tuberculosis Based on Secreted, Species-Specific, Bacterial Small Molecules

Improved biomarkers are needed for tuberculosis. To develop tests based on products secreted by tubercle bacilli that are strictly associated with viability, we evaluated 3 bacterial-derived, species-specific, small molecules as biomarkers: 2 mycobactin siderophores and tuberculosinyladenosine. Using liquid chromatography-tandem mass spectrometry, we demonstrated the presence of 1 or both mycobactins and/or tuberculosinyladenosine in serum and whole lung tissues from infected mice and sputum, cerebrospinal fluid (CSF), or lymph nodes from infected patients but not uninfected controls. Detection of the target molecules distinguished host infection status in 100% of mice with both serum and lung as the target sample. In human subjects, we evaluated detection of the bacterial small molecules (BSMs) in multiple body compartments in 3 patient cohorts corresponding to different forms of tuberculosis. We detected at least 1 of the 3 molecules in 90%, 71%, and 40% of tuberculosis patients' sputum, CSF, and lymph node samples, respectively. In paucibacillary forms of human tuberculosis, which are difficult to diagnose even with culture, detection of 1 or more BSM was rapid and compared favorably to polymerase chain reaction-based detection. Secreted BSMs, detectable in serum, warrant further investigation as a means for diagnosis and therapeutic monitoring in patients with tuberculosis.

Diagnostic accuracy of the rapid urine lipoarabinomannan test for pulmonary tuberculosis among HIV-infected adults in Ghana-findings from the DETECT HIV-TB study

Background

Rapid diagnostic tests are urgently needed to mitigate HIV-associated tuberculosis (TB) mortality. We evaluated diagnostic accuracy of the rapid urine lipoarabinomannan (LAM) test for pulmonary TB and assessed the effect of a two-sample strategy.

Methods

HIV-infected adults eligible for antiretroviral therapy were prospectively enrolled from Korle-Bu Teaching Hospital in Ghana and followed for minimum 6 months. We applied the LAM test on urine collected as a spot and early morning sample. Diagnostic accuracy was analysed for a microbiological TB reference standard based on sputum culture and Gene Xpert MTB/RIF results and for a composite reference standard including clinical follow-up data. Performance of sputum smear microscopy was included for comparison.

Results

Of 469 patients investigated for TB, the LAM test correctly identified 24/55 (44 %) of microbiologically confirmed TB cases. Sensitivity of the LAM test was positively associated with hospitalisation (67 %), Modified Early Warning Score > 4 (57 %) and subsequent death (71 %). LAM test specificity was 95 % increasing to 98 % for the composite reference standard. A two-sample LAM test strategy did not improve test performance. Using concentrated sputum for Ziehl-Neelsen and fluorescence microscopy in combination yielded a sensitivity of 31/55 (56 %) that increased to 35/55 (64 %) when the LAM test was added. Surprisingly, nontuberculous mycobacteria were cultured in 34/469 (7 %) and associated with a positive LAM test (p = 0.008).

Conclusions

LAM test sensitivity was highest in patients with poor prognosis and subsequent death and did not increase with a two-sample strategy. A rigorous sputum microscopy strategy had superior sensitivity, but the simplicity of the LAM test holds operational possibilities as a TB screening method among severely sick patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1151-1) contains supplementary material, which is available to authorized users.

Test characteristics and potential impact of the urine LAM lateral flow assay in HIV-infected outpatients under investigation for TB and able to self-expectorate sputum for diagnostic testing

Background

The commercially available urine LAM strip test, a point-of-care tuberculosis (TB) assay, requires evaluation in a primary care setting where it is most needed. There is currently inadequate data to guide implementation in TB and HIV-endemic settings.

Methods

Adult HIV-infected outpatients with suspected pulmonary TB able to self-expectorate sputum from four primary clinics in South Africa, Zambia and Tanzania underwent diagnostic evaluation [sputum smear microscopy, Xpert-MTB/RIF, and culture (reference standard)] as part of a prospective parent study. Urine LAM testing (grade-2 cut-point) was performed on archived samples. Performance characteristics of LAM alone or in combination with sputum—based diagnostics were evaluated. Potential impact on 2 and 6-month morbidity (TBscore), patient dropout rates, and prognosis (death/ loss to follow-up) were evaluated.

Results

Among 583 participants with suspected TB that were HIV-infected or refused testing, the overall LAM sensitivity (95 % CI; n/N) and in the CD4 ≤ 100 cells/mm³ sub-group was 22.7 % (16.6-28.7; 41/181) and 30.4 % (17.1-43.7; 14/46), respectively. Overall specificity was 93.0 % (90.5-95.6; 361/388). Amongst culture-positive TB cases, adjunctive LAM testing did not improve the sensitivity of either sputum Xpert-MTB/RIF [78.2 % (69.8-86.7; 72/92) versus 76.1 % (67.4-84.8; 70/92), p = 0.7] or smear-microscopy [56.2 % (45.9-66.5; 50/89) versus 43.8 % (33.5-54.1; 39/89), p = 0.1). Clinic-based LAM, as an adjunct to either smear microscopy or Xpert MTB/RIF same-day testing, would neither have decreased patient dropout, nor increased same-day treatment initiation in this clinical setting where same-day chest radiography was available. LAM positivity was associated with 6-month lost-to-follow-up/death (AOR 4.4; p = 0.002) but not TBscore (at baseline or change in TBscore 2-months post-treatment) (p = 0.17).

Conclusions

In African HIV-TB co-infected outpatients able to self-expectorate sputum LAM had limited sensitivity even at low CD4 counts, and offered no significant incremental diagnostic yield over Xpert-MTB/RIF or smear microscopy. In primary care clinics with chest radiography and where empiric TB treatment is common, LAM seems unlikely to improve rates of same-day treatment initiation and patient dropout, however, the ability of LAM to identify patients at high risk of death or lost-to-follow-up may offer important prognostic value.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-0967-z) contains supplementary material, which is available to authorized users.

Is Urinary Lipoarabinomannan the Result of Renal Tuberculosis? Assessment of the Renal Histology in an Autopsy Cohort of Ugandan HIV-Infected Adults

Objective

The detection of urinary lipoarabinomannan (LAM), a mycobacterial cell wall component, is used to diagnose tuberculosis (TB). How LAM enters the urine is not known. To investigate if urinary LAM-positivity is the result of renal TB infection we correlated the outcomes of urinary LAM-antigen testing to renal histology in an autopsy cohort of hospitalized, Ugandan, HIV-infected adults.

Methods

We performed a complete autopsy, including renal sampling, in HIV-infected adults that died during hospitalization after written informed consent was obtained from the next of kin. Urine was collected postmortem through post-mortem catheterisation or by bladder puncture and tested for LAM with both a lateral flow assay (LFA) and an ELISA assay. Two pathologists assessed the kidney histology. We correlated the LAM-assay results and the histology findings.

Results

Of the 13/36 (36%) patients with a positive urinary LAM ELISA and/or LFA, 8/13 (62%) had renal TB. The remaining 5 LAM-positive patients had disseminated TB without renal involvement. Of the 23 LAM-negative patients, 3 had disseminated TB without renal involvement. The remaining LAM-negative patients had no TB infection and died mostly of fungal and bacterial infections. LAM LFA had a sensitivity of 81% and specificity of 100% to diagnose TB at any location, and the LAM ELISA a sensitivity of 63% and a specificity of 100%. 54% (7/13) LAM LFA-positive patients were not on anti-TB treatment at the time of death.

Conclusion

Renal TB infection explained LAM-positivity in the majority of patients. Patients with disseminated TB without renal involvement can also be diagnosed with LAM. This suggests that other mechanisms that lead to urinary LAM-positivity exist in a minority of patients.

Diagnostic accuracy of a rapid urine lipoarabinomannan test for tuberculosis in HIV-infected adults

OBJECTIVE

In settings of high HIV prevalence, tuberculosis control and patient management are hindered by lack of accurate, rapid tuberculosis diagnostic tests that can be performed at point-of-care. The Determine TB LAM Ag (TB LAM) test is a lateral flow immunochromatographic test for detection of mycobacterial lipoarabinomannan (LAM) in urine. Our objective was to determine sensitivity and specificity of the TB LAM test for tuberculosis diagnosis.

DESIGN

Prospective diagnostic accuracy study.

SETTING

Hospital and outpatient settings in Uganda and South Africa.

PARTICIPANTS

HIV-infected adults with tuberculosis symptoms and/or signs.

METHODS

Participants provided a fresh urine specimen for TB LAM testing, blood for mycobacterial culture, and 2 respiratory specimens for smear microscopy and mycobacterial culture.

MAIN OUTCOME MEASURES

For the TB LAM test, sensitivity in participants with culture-positive tuberculosis and specificity in participants without tuberculosis.

RESULTS

A total of 1013 participants were enrolled. Among culture-positive tuberculosis patients, the TB LAM test identified 136/367 (37.1%) overall and 116/196 (59.2%) in the group with CD4 ≤100 cells per cubic millimeter. The test was specific in 559/573 (97.6%) patients without tuberculosis. Sensitivity of the urine TB LAM test plus sputum smear microscopy was 197/367 (53.7%) overall and 133/196 (67.9%) among those with CD4 ≤100. CD4 ≤50 [adjusted odds ratio (AOR), 6.2; P < 0.001] or 51-100 (AOR, 7.1; P < 0.001), mycobacteremia (AOR, 6.1; P < 0.01) and hospitalization (AOR, 2.6; P = 0.03) were independently associated with a positive TB LAM test.

CONCLUSIONS

In HIV-positive adults with CD4 ≤100, the TB LAM urine test detected over half of culture-positive tuberculosis patients, in <30 minutes and without the need for equipment or reagents.

Urine lipoarabinomannan point-of-care testing in patients affected by pulmonary nontuberculous mycobacteria--experiences from the Danish Cystic Fibrosis cohort study

Background

The urine lipoarabinomannan (LAM) strip test has been suggested as a new point-of-care test for active tuberculosis (TB) among human immunodeficiency virus (HIV) infected individuals. It has been questioned if infections with nontuberculous mycobacteria (NTM) affect assay specificity. We set forth to investigate if the test detects LAM in urine from a Danish cystic fibrosis (CF) population characterized by a high NTM prevalence and negligible TB exposure.

Method

Patients followed at the Copenhagen CF Center were comprehensively screened for pulmonary NTM infection between May 2012 and December 2013. Urine samples were tested for LAM using the 2013 Determine™ TB LAM Ag strip test.

Results

Three-hundred and six patients had a total of 3,322 respiratory samples cultured for NTM and 198 had urine collected (65%). A total of 23/198 (12%) had active pulmonary NTM infection. None had active TB. The TB-LAM test had an overall positive rate of 2.5% applying a grade 2 cut-point as positivity threshold, increasing to 10.6% (21/198) if a grade 1 cut-point was applied. Among patients with NTM infection 2/23 (8.7%) had a positive LAM test result at the grade 2 cut-point and 9/23 (39.1%) at the grade 1 cut -point. Test specificity for NTM diagnosis was 98.3% and 93.1 for grade 2 and 1 cut-point respectively.

Conclusions

This is the first study to assess urine LAM detection in patients with confirmed NTM infection. The study demonstrated low cross-reactivity due to NTM infection when using the recommended grade 2 cut-point as positivity threshold. This is reassuring in regards to interpretation of the LAM test for TB diagnosis in a TB prevalent setting. The test was not found suitable for NTM detection among patients with CF.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0655-4) contains supplementary material, which is available to authorized users.

Mannosylated lipoarabinomannan in serum as a biomarker candidate for subclinical bovine tuberculosis

Background

Early and unambiguous detection of bovine tuberculosis (bTB), a significant disease of cattle worldwide, is necessary to control the spread of infection to other animals and humans. Current testing strategies are laborious, time consuming and heavily reliant on host responses that do not distinguish bTB from other mycobacteria. We report the presence of a pathogen signature, liparabinomannan (LAM), as a potential biomarker for bTB infection.

Findings

Fifty-five animals (uninfected [n = 33], bTb [n = 10] and exposed cases [n = 12]) from a well characterized bovine serum repository were screened for the presence of LAM using a commercially available ELISA. Analysis showed that LAM had a sensitivity of 100% and a specificity of 91.7% for bTB detection (bTB positive versus bTB exposed animals).

Conclusion

LAM detection easily separated bTB infected animals from bTB exposed and negative controls. We propose that pathogen related markers, such as LAM, should be included with current testing strategies as a battery diagnostic for bTB.

Electronic supplementary material

The online version of this article (doi:10.1186/1756-0500-7-559) contains supplementary material, which is available to authorized users.

Prognostic value of a quantitative analysis of lipoarabinomannan in urine from patients with HIV-associated tuberculosis

BACKGROUND

Detection of the mycobacterial cell wall antigen lipoarabinomannan (LAM) in urine can be used to diagnose HIV-associated tuberculosis (TB) using a qualitative (positive/negative) read-out. However, it is not known whether the quantity of LAM present in urine provides additional prognostic information.

METHODS/FINDINGS

Consecutively recruited adult outpatients initiating antiretroviral therapy (ART) in South Africa were investigated for TB regardless of clinical symptoms using sputum smear microscopy and liquid culture (reference standard). Urine samples were tested using the Clearview TB-ELISA for LAM and the Xpert MTB/RIF assay. The ELISA optical densities (OD) were used as a quantitative assessment of urine LAM. Among 514 patients with complete sputum and urine LAM OD results, culture-confirmed TB was diagnosed in 84 patients. Twenty-three (27.3%) were LAM-positive with a median LAM OD of 0.68 (IQR 0.16-2.43; range, 0.10-3.29) and 61 (72.6%) were LAM negative (LAM OD <0.1 above background). Higher LAM ODs were associated with a range of prognostic indices, including lower CD4 cell counts, lower haemoglobin levels, higher blood neutrophil counts and higher mycobacterial load as assessed using both sputum and urine samples. The median LAM OD among patients who died was more than 6.8-fold higher than that of patients who remained alive at 3 months (P<0.001). The small number of deaths, however, precluded adequate assessment of mortality risk stratified according to urine LAM OD.

CONCLUSIONS

In patients with HIV-associated TB, concentrations of LAM in urine were strongly associated with a range of poor prognostic characteristics known to be associated with mortality risk. Urine LAM assays with a semi-quantitative (negative vs. low-positive vs. high-positive) read-out may have improved clinical utility over assays with a simple binary result.

Determine TB-LAM lateral flow urine antigen assay for HIV-associated tuberculosis: recommendations on the design and reporting of clinical studies

Detection of the Mycobacterium tuberculosis cell wall antigen lipoarabinomannan (LAM) in urine permits diagnoses of tuberculosis (TB) to be made in HIV-infected patients with advanced immunodeficiency. This can be achieved at the point-of-care within just 30 minutes using the Determine TB-LAM, which is a commercially available, lateral-flow urine 'strip test' assay. The assay has been shown to have useful diagnostic accuracy in patients enrolling in antiretroviral treatment services or in HIV-infected patients requiring admission to hospital medical wards in sub-Saharan Africa. Such patients have high mortality risk and have most to gain from rapid diagnosis of TB and immediate initiation of treatment. However, few studies using this assay have yet been reported and many questions remain concerning the correct use of the assay, interpretation of results, the role of the assay as an add-on test within existing diagnostic algorithms and the types of further studies needed. In this paper we address a series of questions with the aim of informing the design, conduct and interpretation of future studies. Specifically, we clarify which clinical populations are most likely to derive benefit from use of this assay and how patients enrolled in such studies might best be characterised. We describe the importance of employing a rigorous microbiological diagnostic reference standard in studies of diagnostic accuracy and discuss issues surrounding the specificity of the assay in different geographical areas and potential cross-reactivity with non-tuberculous mycobacteria and other organisms. We highlight the importance of careful procedures for urine collection and storage and the critical issue of how to read and interpret the test strips. Finally, we consider how the assay could be used in combination with other assays and outline the types of studies that are required to build the evidence base concerning its use.

Modification of clearview tuberculosis (TB) enzyme-linked immunosorbent assay for TB patients not infected with HIV

Diagnosis of active tuberculosis by detection of urinary lipoarabinomannan (uLAM) from Mycobacterium tuberculosis is an attractive approach. Concentrating urine 100-fold allowed quantitation of uLAM at levels equal to picograms/ml of nonconcentrated urine. The approach of concentrating urine 100-fold improved the clinical sensitivity of the Clearview TB enzyme-linked immunosorbent assay (ELISA) from 7% to 57% yet impaired its specificity from 97% to 89%. (This study has been registered at University Hospital of Turku under registration no. 47/180/2009, Helsinki University Central Hospital under 149/2010, University Hospital of Kuopio under 105/2010, and China Medical University Hospital, Taichung, under DMR-99-IRB-075-2.).

Undiagnosed tuberculosis among HIV clinic attendees: association with antiretroviral therapy and implications for intensified case finding, isoniazid preventive therapy, and infection control

OBJECTIVES

Initiation of antiretroviral therapy (ART) and the 3I's are strategies to prevent HIV-associated tuberculosis (TB). We describe factors associated with undiagnosed TB among HIV-infected patients attending an HIV clinic in South Africa and discuss implications for the 3 Is.

DESIGN

Convenience sample of HIV clinic attendees.

METHODS

HIV-infected participants were assessed for TB using a symptom screen, sputum-smear microscopy, sputum and blood mycobacterial culture, fine needle aspiration of enlarged lymph nodes, and chest radiography.

RESULTS

Four hundred twenty-two participants were enrolled. The median age and CD4+ T-cell count were 37 years [interquartile range (IQR): 31-44 years] and 215 cells per microliter (IQR: 107-347 cells/μL). Forty-seven percent had been on ART for a median duration of 8 months (IQR: 3.3-22.8 months). Three hundred sixty-one participants (85.6%) reported TB symptoms. Twenty-seven participants (6.4%) met criteria for bacteriologically confirmed TB and 50 (11.6%) for any form of TB. Bacteriologically confirmed TB was associated with CD4+ T-cell counts ≤100 cells per microliter (odds ratio: 5.05, 95% confidence interval: 1.69 to 15.12) when compared with CD4+ T-cell counts >200 cells per microliter and hemoglobin {hemoglobin < 10 g/dL [odds ratio 3.12 (95% confidence interval: 1.26 to 7.72)]}.

CONCLUSIONS

Undiagnosed TB among HIV-infected ambulatory patients was associated with low CD4+ T-cell counts regardless of ART status. TB screening algorithms which include CD4+ T-cell count and hemoglobin testing may be an effective way to identify HIV-infected clinic attendees at highest risk of undiagnosed TB. Isoniazid preventive therapy and TB infection control are essential for reducing occurrence of HIV-associated TB even after ART initiation.

Point-of-care detection of lipoarabinomannan (LAM) in urine for diagnosis of HIV-associated tuberculosis: a state of the art review

Detection of Mycobacterium tuberculosis antigens in urine is attractive as a potential means of diagnosing tuberculosis (TB) regardless of the anatomical site of disease. The most promising candidate antigen is the cell wall lipopolysaccharide antigen lipoarabinomannan (LAM), which has been used to develop commercially available enzyme-linked immunosorbent assays. Although highly variable diagnostic accuracy has been observed in different clinical populations, it is now clear that this assay has useful sensitivity for diagnosis of HIV-associated TB in patients with advanced immunodeficiency and low CD4 cell counts. Thus, this assay is particularly useful when selectively used among patients enrolling in antiretroviral treatment services or in HIV-infected patients requiring admission to hospital medical wards. These are the very patients who have the highest mortality risk and who stand to gain the most from rapid diagnosis, permitting immediate initiation of TB treatment. A recently developed low-cost, lateral-flow (urine 'dip-stick') format of the assay provides a result within 30 minutes and is potentially a major step forward as it can be used at the point-of-care, making the possibility of immediate diagnosis and treatment a reality. This paper discusses the likely utility of this point-of-care assay and how it might best be used in combination with other diagnostic assays for TB. The many further research studies that are needed on this assay are described. Consideration is particularly given to potential reasons for the variable specificity observed in existing field evaluations of LAM ELISAs. Whether this might be related to the assay itself or to the challenges associated with study design is discussed.

Clinical research and development of tuberculosis diagnostics: moving from silos to synergy

The development, evaluation, and implementation of new and improved diagnostics have been identified as critical needs by human immunodeficiency virus (HIV) and tuberculosis researchers and clinicians alike. These needs exist in international and domestic settings and in adult and pediatric populations. Experts in tuberculosis and HIV care, researchers, healthcare providers, public health experts, and industry representatives, as well as representatives of pertinent US federal agencies (Centers for Disease Control and Prevention, Food and Drug Administration, National Institutes of Health, United States Agency for International Development) assembled at a workshop proposed by the Diagnostics Working Group of the Federal Tuberculosis Taskforce to review the state of tuberculosis diagnostics development in adult and pediatric populations.

Test characteristics of urinary lipoarabinomannan and predictors of mortality among hospitalized HIV-infected tuberculosis suspects in Tanzania

Background

Tuberculosis is the most common cause of death among patients with HIV infection living in tuberculosis endemic countries, but many cases are not diagnosed pre-mortem. We assessed the test characteristics of urinary lipoarabinomannan (LAM) and predictors of mortality among HIV-associated tuberculosis suspects in Tanzania.

Methods

We prospectively enrolled hospitalized HIV-infected patients in Dar es Salaam, with ≥2 weeks of cough or fever, or weight loss. Subjects gave 2 mLs of urine to test for LAM using a commercially available ELISA, ≥2 sputum specimens for concentrated AFB smear and solid media culture, and 40 mLs of blood for culture.

Results

Among 212 evaluable subjects, 143 (68%) were female; mean age was 36 years; and the median CD4 count 86 cells/mm³. 69 subjects (33%) had culture confirmation of tuberculosis and 65 (31%) were LAM positive. For 69 cases of sputum or blood culture-confirmed tuberculosis, LAM sensitivity was 65% and specificity 86% compared to 36% and 98% for sputum smear. LAM test characteristics were not different in patients with bacteremia but showed higher sensitivity and lower specificity with decreasing CD4 cell count. Two month mortality was 64 (53%) of 121 with outcomes available. In multivariate analysis there was significant association of mortality with absence of anti-retroviral therapy (p = 0.004) and a trend toward association with a positive urine LAM (p = 0.16). Among culture-negative patients mortality was 9 (75%) of 12 in LAM positive patients and 27 (38%) of 71 in LAM negative patients (p = 0.02).

Conclusions

Urine LAM is more sensitive than sputum smear and has utility for the rapid diagnosis of culture-confirmed tuberculosis in this high-risk population. Mortality data raise the possibility that urine LAM may also be a marker for culture-negative tuberculosis.

Diagnostic accuracy of a urine lipoarabinomannan strip-test for TB detection in HIV-infected hospitalised patients

Lack of point-of-care tests for tuberculosis (TB) result in diagnostic delay, and increased mortality and healthcare-related costs. The urine Determine(TM) TB-LAM point-of-care strip-test was evaluated in 335 prospectively-recruited hospitalised patients with suspected TB-HIV co-infection (group 1) and from 88 HIV-infected hospitalised patients with non-TB diagnoses (group 2). Cut-off point-specific analyses were performed using: 1) a microbiological reference standard (culture positive versus negative); and 2) a composite reference standard (exclusion of patients with clinical-TB from the culture-negative group). Using the microbiological reference and the manufacturer-recommended grade-1 cut-off point, LAM sensitivity and specificity was 66% (95% CI 57-74%). By contrast, using the composite reference sensitivity was 60% (95% CI 53-67%) and specificity improved to 96% (95% CI 89-100%) (p=0.001). The same pattern was seen when the grade-2 cut-off point was used (specificity 75% versus 96%; p=0.01). In group two patients specificity was poor using the grade-1 cut-off point, but improved significantly when the grade-2 cut-off point was used (90% versus 99%; p=0.009). The grade-2 cut-off point also offered superior inter-reader reliability (p=0.002). Sensitivity was highest in those with a CD4 <200 cells per mL. LAM combined with smear-microscopy was able to rule-in TB in 71% of Mycobacterium tuberculosis culture-positive patients. This preliminary study indicates that the LAM strip-test may be a potentially useful rapid rule-in test for TB in hospitalised patients with advanced immunosuppression. The grade 2, but not the manufacturer-recommended grade 1 cut-off point, offered superior rule-in utility and inter-reader reliability. Larger studies to evaluate cut-off points and diagnostic accuracy are urgently required.

Diagnostic accuracy of a low-cost, urine antigen, point-of-care screening assay for HIV-associated pulmonary tuberculosis before antiretroviral therapy: a descriptive study

Background

The diagnostic accuracy of sputum smear microscopy and routine chest radiology for HIV-associated tuberculosis is poor, and culture-based diagnosis is slow, expensive, and is unavailable in most resource-limited settings. We assessed the diagnostic accuracy of a urine antigen test Determine TB-LAM Ag (Determine TB-LAM; Alere, Waltham, MA, USA) for screening for HIV-associated pulmonary tuberculosis before antiretroviral therapy (ART).

Methods

In this descriptive study, consecutive adults referred to a community-based ART clinic in Gugulethu township, South Africa, were all screened for tuberculosis by obtaining sputum samples for fluorescence microscopy, automated liquid culture (gold-standard test), and Xpert MTB/RIF assays (Cepheid, Sunnyvale, CA, USA) and urine samples for the Clearview TB-ELISA (TB-ELISA; Alere, Waltham, MA, USA) and Determine TB-LAM test. Patients with Mycobacterium tuberculosis cultured from one or more sputum samples were defined as cases of tuberculosis. The diagnostic accuracy of Determine TB-LAM used alone or combined with sputum smear microscopy was compared with that of sputum culture and the Xpert MTB/RIF assay for all patients and subgroups of patients stratified by CD4 cell count.

Findings

Patients were recruited between March 12, 2010, and April 20, 2011. Of 602 patients enrolled, 542 were able to provide one or more sputum samples, and 94 had culture-positive tuberculosis (prevalence 17·4%, 95% CI 14·2–20·8). Complete results from all tests were available for 516 patients (median CD4 count, 169·5 cells per μL; IQR 100–233), including 85 culture-positive tuberculosis, 24 of whom (28·2%, 95% CI 19·0–39·0) had sputum smear-positive disease. Determine TB-LAM test strips provided results within 30 min. Agreement was very high between two independent readers of the test strips (κ=0·97) and between the test strips and TB-ELISA (κ=0·84). Determine TB-LAM had highest sensitivity at low CD4 cell counts: 66·7% (95% CI 41·0–86·7) at <50 cells per μL, 51·7% (32·5–70·6) at <100 cells per μL, and 39·0% (26·5–52·6) at <200 cells per μL; specificity was greater than 98% for all strata. When combined with smear microscopy (either test positive), sensitivity was 72·2% (95% CI 46·5–90·3) at CD4 counts less than 50 cells per μL, 65·5% (45·7–82·1) at less than 100 cells per μL, and 52·5% (39·1–65·7) at less than 200 cells per μL, which did not differ statistically from the sensitivities obtained by testing a single sputum sample with the Xpert MTB/RIF assay.

Interpretation

Determine TB-LAM is a simple, low-cost, alternative to existing diagnostic assays for tuberculosis screening in HIV-infected patients with very low CD4 cell counts and provides important incremental yield when combined with sputum smear microscopy.

Funding

Wellcome Trust.