Urine-based diagnostic tests for tuberculosis: a scoping review highlighting unmet diagnostic needs.

To investigate the diagnostic value of a novel high-sensitivity urine lipoarabinomannan (LAM) test (chemiluminescence-based) for active tuberculosis in the general population. A retrospective study was conducted on 250 clinical suspected tuberculosis patients who were HIV-negative and visited the Fourth People’s Hospital of Foshan from January 2022 to December 2022. Among them, there were 135 cases of pulmonary tuberculosis, 34 cases of extrapulmonary tuberculosis, and 81 cases of non-tuberculosis. Urine samples were collected for LAM antigen detection before treatment, and laboratory data of sputum smear acid-fast staining (smear method), sputum culture, and GeneXpert method were collected. Using clinical diagnosis as the reference standard, the diagnostic efficacy of 4 methods for detecting active tuberculosis was evaluated. For the 135 cases of pulmonary tuberculosis, the sensitivity of sputum smears, sputm culture, sputm GeneXpert method, and urine LAM were 29.6% (40/135), 45.9% (62/135), 59.3% (80/135), and 51.9% (70/135), respectively. The combination of LAM + GeneXpert and LAM + culture had the highest sensitivity for detecting active pulmonary tuberculosis, which were 71.0% and 78.2%, respectively. For the detection of sputum culture-negative pulmonary tuberculosis, the positive rates of smear, GeneXpert, and LAM were 0.0% (0/73), 53.4% (39/73), and 52.1% (38/73), respectively. LAM + smear and LAM + Genexpert could detect 52.1% and 68.5% of sputum culture-negative patients, respectively. The high-sensitivity urine LAM test holds promise for tuberculosis diagnosis in the general population. It demonstrates high-sensitivity, enabling the detection of sputum culture-negative pulmonary tuberculosis patients. Furthermore, when combined with existing methods, it can enhance the overall detection rate.

Background Non-respiratory biomarkers for tuberculosis (TB), such as the urinary lipoarabinomannan (LAM) antigen, are crucial for diagnosing TB in at-risk pediatric populations. Currently available urine assays to detect LAM as a diagnostic test for TB have limited sensitivity in pediatric populations. We aimed to evaluate the Ceres TB-Nanotrap as a urine concentration step to augment detection of LAM antigens in urine. Methods Urine specimens were obtained from children 1-18 years of age with presumptive TB (cases) and non-TB controls from outpatient clinics in Karachi, Pakistan. An Alere lateral flow (LF)-LAM test was performed before and after concentrating urine with magnetic TB-Nanotrap particles. Band intensity was measured via visual grading and digital quantification (using Image-J software) and performance characteristics were calculated for unconcentrated and concentrated urine. Results Urine LAM sensitivity by visual grading was 4.5% (95% Confidence Interval [CI]: 0.3 – 18.5) pre-concentration and 50.0% (95% CI 30.0 – 70.0) post-concentration. Sensitivity by digital quantification was 0.0% (95% CI 0.0 – 15.4) pre-concentration and 63.9% (95% CI 42.8 – 81.4) post-concentration. Specificity was high with both methods (visual grading 90.0% [62.8 – 99.4] pre-concentration, 90.0% [62.8 – 99.4] post-concentration; digital analysis 80.0% [44.4 – 97.5], 90.0% [62.8 – 99.4] respectively). For specimens from TB cases, digital analysis showed an increase in median LF-LAM band intensity from 0.0 arbitrary units (AU) (IQR 0.00 – 32.5) in unconcentrated samples to 98.4 AU (IQR 34.9 – 212.2) in concentrated samples. Conclusion Concentration with TB-Nanotrap greatly increased sensitivity of urine LAM detection without change in specificity. Digital quantitative analysis further increased sensitivity. Incorporating this concentration step into urine LAM may improve diagnostic accuracy of the test. Use of digital quantitative analysis of urine LAM may increase sensitivity and allow for more precise quantification of urine LAM. Future work should explore the use of TB-Nanotrap concentration in other populations that are challenging to diagnose. Disclosures All Authors: No reported disclosures

The diagnosis of tuberculosis (TB) in HIV-infected patients is challenging. Both a urinary lipoarabinomannan (LAM) test (Alere TB LAM) and GeneXpert-MTB/RIF (Xpert) are useful for the diagnosis of TB. However, how to optimally integrate Xpert and LAM tests into clinical practice algorithms remain unclear. We performed a post hoc analysis of 561 HIV-infected sputum-expectorating patients (median CD4 count of 130 cells/ml) from a previously published randomized controlled trial evaluating the LAM test in hospitalized HIV-infected patients with suspected TB. We evaluated 5 different diagnostic strategies using sputum culture as a reference standard (Xpert alone, LAM alone, sequential Xpert followed by LAM and vice versa [LAM in Xpert-negative patients and Xpert in LAM-negative patients], and both tests concurrently [LAM + Xpert]). A cost-consequence analysis was performed. Strategy-specific sensitivity and specificity, using culture as a reference, were similar with the Xpert-only and sequential and concurrent strategies. However, when any positive TB-specific test was used as a reference, the incremental yield of LAM over Xpert was 29.6% (45/152) and that of Xpert over LAM was 75% (84/11). The incremental yield of LAM increased with decreasing CD4 count. The costs per TB case diagnosed were similar for the sequential and concurrent strategies ($1,617 to $1,626). In sputum-expectorating hospitalized patients with advanced HIV and access to both tests, concurrent testing with Xpert and LAM may be the best strategy for diagnosing TB. These data inform clinical practice in settings where TB and HIV are endemic.

BackgroundThe urine lipoarabinomannan (LAM) antigen test is a tuberculosis (TB) diagnostic test with highest sensitivity in individuals with advanced human immunodeficiency virus (HIV). Its role in TB diagnostic algorithms for HIV-positive outpatients remains unclear.MethodsThe AIDS Clinical Trials Group (ACTG) A5274 trial demonstrated that empiric TB therapy did not improve 24-week survival compared to isoniazid preventive therapy (IPT) in TB screen–negative HIV-positive adults initiating antiretroviral therapy with CD4 counts <50 cells/µL. Retrospective LAM testing was performed on stored urine obtained at baseline. We determined the proportion of LAM-positive participants and conducted modified intent-to-treat analysis excluding LAM-positive participants to determine the effect on 24-week survival, TB incidence, and time to TB using Kaplan-Meier method.ResultsA5274 enrolled 850 participants; 53% were male and the median CD4 count was 18 (interquartile range, 9–32) cells/µL. Of the 850, 566 (67%) had LAM testing (283 per arm); 28 (5%) were positive (21 [7%] and 7 [2%] in the empiric and IPT arms, respectively). Of those LAM-positive, 1 participant in each arm died and 5 of 21 and 0 of 7 in empiric and IPT arms, respectively, developed TB. After excluding these 28 cases, there were 19 and 21 deaths in the empiric and IPT arms, respectively (P = .88). TB incidence remained higher (4.6% vs 2%, P = .04) and time to TB remained faster in the empiric arm (P = .04).ConclusionsAmong outpatients with advanced HIV who screened negative for TB by clinical symptoms, microscopy, and Xpert testing, LAM testing identified an additional 5% of individuals with TB. Positive LAM results did not change mortality or TB incidence.

We assessed the role of urine lipoarabinomannan (LAM) grade and a second LAM test for HIV-associated pulmonary tuberculosis (TB) screening in outpatient clinics in South Africa. We enrolled newly diagnosed HIV-infected adults (≥18 years) at 4 clinics, excluding those on TB therapy. Participants provided sputum for acid-fast bacilli (AFB) microscopy and culture. Nurses conducted 2 rapid urine LAM tests at the point-of-care and graded positive results from low (faint) to high (5+). Culture-confirmed pulmonary TB was the gold standard. We used area under receiver operating curves (AUROC) to compare screening strategies. Among 320 HIV-infected adults, median CD4 was 248 cells per cubic millimeter (interquartile range, 107-379/mm); 54 (17%) were TB culture positive. Fifty-two (16%) of all participants were LAM positive by either test; correlation between LAM tests was high. Among 10 "faint" positive results, 2 (20%) had culture-positive TB. Using ≥1+ LAM grade as positive, 1 LAM test had sensitivity of 41% [95% confidence interval (CI): 28% to 55%] and specificity of 92% (95% CI: 88% to 95%). A 2 LAM test strategy had a sensitivity of 43% (95% CI: 29% to 57%). One LAM test ≥1+ grade (AUROC = 0.66; 95% CI: 0.60 to 0.73) was significantly better than sputum AFB alone. The optimal strategy was sequentially performing 1 LAM test followed by sputum AFB if LAM grade <1+ (AUROC = 0.70; 95% CI: 0.63 to 0.77), which had sensitivity of 48% (95% CI: 34% to 62%) and specificity of 91% (95% CI: 87% to 94%). In this clinic-based study, "faint" line was a false-positive second urine LAM test added no value, and an optimal screening strategy was 1 LAM test followed by sputum AFB microscopy for urine LAM-negative people.

To assess the diagnostic accuracy of the urine lipoarabinomannan (LAM) test among ambulatory HIV-infected persons. Cross-sectional. HIV-infected persons consecutively presenting to the HIV Clinic at Tembisa Main Clinic in Ekhuruleni, South Africa, were screened for symptoms of tuberculosis (TB) and asked to provide sputum and blood samples for smears for acid-fast bacilli and mycobacterial culture and a urine specimen for a LAM enzyme-linked immunosorbent assay. Fine needle aspirates were obtained from participants with enlarged lymph nodes and sent for histopathology. Nonpregnant participants underwent chest x-ray. : Four hundred twenty-two HIV-infected participants were enrolled with median age 37 years (interquartile range: 31-44 years), median CD4+ T-cell count 215 cells per microliter (interquartile range: 107-347 cells/μL), and 212 (50%) receiving antiretroviral therapy. Thirty (7%) had active TB: 18 with only pulmonary TB, 5 with only extrapulmonary TB, and 7 with both pulmonary TB and extrapulmonary TB. Twenty-seven percent [95% confidence interval (CI): 12% to 48%] of TB cases were sputum acid-fast bacilli positive. The sensitivity and specificity of the urine LAM compared with the gold standard of positive bacteriology or histopathology were 32% (95% CI: 16% to 52%) and 98% (95% CI: 96% to 99%), respectively. Urine LAM had higher sensitivity in TB cases with higher bacillary burdens, though these differences were not statistically significant. The sensitivity of urine LAM testing is inadequate to replace mycobacterial culture. In contrast to prior research on the urine LAM, this study was conducted among less sick, ambulatory HIV-infected patients presenting for routine care.

Development of a non-sputum test using readily-obtainable biospecimens remains a global priority for tuberculosis (TB) control. We quantified lipoarabinomannan (LAM) concentrations, a pathogen biomarker for Mycobacterium tuberculosis, in urine, plasma and serum for real-world diagnostic accuracy of pulmonary TB among people living with and without HIV. We conducted a prospective diagnostic study among adults with TB symptoms in South Africa. We measured LAM concentrations in time-matched urine, plasma and serum with an electrochemiluminescence immunoassay using two capture antibodies (FIND 28 and S4-20). From the completed cohort, we randomly selected 210 participants (2 cases: 1 control) based on sensitivity estimates, and we compared diagnostic accuracy of LAM measurements against the microbiological reference standard. Urine and blood specimens from 210 of 684 adults enrolled were tested for LAM. Among 138TB-positive adults (41% female), median urine LAM was 137pg/mL and 52pg/mL by FIND 28 and S4-20, respectively. Average LAM concentrations were highest in HIV-positive participants with CD4+ T cells <200cells/mm3. Urine LAM by S4-20 achieved diagnostic sensitivity of 62% (95% CI: 53%-70%) and specificity of 99% (95% CI: 96%-100%). Plasma and serum LAM by FIND 28 showed similar sensitivity (70%, 95% CI: 62%-78%) and comparable specificities (90%, 95% CI: 82%-97%; 94%, 95% CI: 88%-99%). Diagnostic sensitivity of urine LAM by S4-20 was higher among participants without HIV (41%, 95% CI: 24%-61%) compared to HIV-positive participants with CD4 ≥200cells/mm3 (20%, 95% CI: 8%-39%). Detection of LAM was achievable in non-sputum specimens for pulmonary TB, but additional analyte concentration or signal amplification may be required to achieve diagnostic accuracy targets. Bill and Melinda Gates Foundation.

To assess the utility of urine lipoarabinomannan (LAM) detection as a diagnostic screening test for tuberculosis (TB) in HIV-infected patients with advanced immuno deficiency and high prevalence of sputum smear-negative pulmonary disease. Cross-sectional survey. Unselected adults enrolling for antiretroviral therapy (ART) in a South African clinic were screened for TB with two sputum samples for fluorescence microscopy and mycobacterial liquid culture. LAM was measured in urine samples using a commercially available enzyme-linked immunosorbent assay. Sputum culture-positive TB was diagnosed in 58 patients (median CD4 cell count=78 cells/microliter) out of 235 patients screened (TB prevalence=0.25). Cultures were identified as positive after a mean of 24 days (SD=9 days). The sensitivity of sputum microscopy was just 0.14 (specificity=1.00), whereas that of LAM in concentrated urine was 0.38 (P<0.01; specificity=1.00). In those with CD4 cell counts of less than 50, 50-100 and more than 150 cells/microliter, the LAM assay sensitivities were 0.67, 0.41 and 0.13, respectively. Corresponding values for the combined use of the LAM assay and microscopy were 0.67, 0.53 and 0.21, respectively. Among TB patients, detectable LAM was very strongly associated with low CD4 cell counts and advanced clinical stage. All patients who developed TB immune reconstitution disease (n=5) had detectable urinary LAM at baseline. The LAM assay has substantially superior sensitivity to sputum microscopy as a routine diagnostic TB screening test among patients with CD4 cell counts less than 100 cells/microliter. In one half of such patients, this assay could reduce the mean time to diagnosis by approximately 3 weeks. Furthermore, detectable urinary LAM may predict the development of TB immune reconstitution disease.

BackgroundUrine lateral flow lipoarabinomannan (LF-LAM) is a point-of-care tuberculosis (TB) test for patients with human immunodeficiency virus (HIV). Xpert MTB/RIF Ultra (Ultra) has improved sensitivity on sputum compared with the previous generation of Xpert and may improve diagnostic yield for TB on urine-based testing.MethodsWe conducted a diagnostic accuracy study in East London, South Africa. Adults with HIV hospitalized with ≥1 W4SS (World Health Organization–recommended 4-symptom screen) or clinical concern for TB were enrolled; TB cultures were performed on blood, sputum, and urine. Unprocessed urine was tested with LF-LAM and Ultra on the pellet of 15 mL centrifuged urine. The primary outcome was sensitivity of urine Ultra compared with LF-LAM, with microbiological TB (positive TB culture or molecular test, excluding urine Ultra) as the reference. Secondary outcomes included specificity and diagnostic yield.ResultsTwo hundred thirty-eight participants were enrolled with a median CD4 count of 76 cells/mm3. Microbiological TB was diagnosed in 62 (26%). Using microbiological TB as the reference, sensitivity of LF-LAM and urine Ultra was 45% (95% confidence interval, 32–58) and 70% (95% CI, 57–81; McNemar P = .0013); specificity was 93% (95% CI, 81–99) and 100% (95% CI, 92–100; McNemar P = .25). Diagnostic yields for microbiological TB were 34% for sputum Ultra, 45% for urine LF-LAM, 68 for urine Ultra, and 73% for urine LF-LAM and urine Ultra combined.ConclusionsCombined urine-based testing (Ultra + LF-LAM) identified nearly three-quarters of medical inpatients with HIV with microbiological TB. Urine Ultra had significantly improved sensitivity compared with LF-LAM.

BackgroundThe urinary lipoarabinomannan (LAM) assay has emerged as a promising tool for tuberculosis (TB) diagnosis and treatment monitoring. This study aimed to evaluate the diagnostic and monitoring performance of LAM compared to Acid-fast bacilli (AFB), Mycobacteria Growth Indicator Tube (MGIT), and GeneXpert, and to establish its clinical utility in a stratified TB population.MethodsA prospective cohort study included TB patients stratified by AFB/MGIT status into three groups. Diagnostic accuracy was tested against composite reference standard (CRS). Early monitoring performance was assessed via serial LAM measurements during 12-week treatment. ROC/KM/Cox analyses determined optimal thresholds and predictors of LAM conversion.ResultsAgainst CRS, LAM demonstrated a sensitivity of 58.75%, which was numerically higher than AFB smear (45.00%, p = 0.082) and comparable to MGIT culture (58.75%, p = 1.00), but numerically lower than GeneXpert (61.25%, p = 0.205). In the early monitoring phase, LAM showed sustained positivity in 11.54–51.72% at week 12, compared to <15% for other methods. The diagnostic-monitoring quadrant analysis revealed LAM’s optimal positioning for monitoring (mean conversion time 4.63–11.49 weeks), compared to 0–8.25 weeks for other methods. A combined model incorporating baseline PreLAM and week 4 change (ΔLAM) showed the highest predictive value for 12 weeks conversion (AUC = 0.871–0.943). Multivariate cox analysis identified ΔLAM as independent predictors in total cohort (HR = 0.013, p = 0.001) and double positive group (HR = 0.020, p = 0.002).ConclusionUrinary LAM serves as a dual-role biomarker, providing moderate diagnostic sensitivity and dynamic monitoring signals reflecting early bacillary response to therapy. The PreLAM+ΔLAM model enables early treatment response assessment for personalized therapy.

Xpert MTB/RIF ('Xpert') and urinary lipoarabinomannan (LAM) assays offer rapid tuberculosis (TB) diagnosis, but have suboptimal sensitivity when used individually in HIV-positive patients. The yield of these tests used in combination for the diagnosis of active TB among HIV-infected TB suspects is unknown. Study of comparative diagnostic accuracy nested into a prospective study of HIV-infected individuals with signs and/or symptoms of TB in Uganda. Xpert testing of archived sputum was conducted for culture-confirmed TB cases and TB suspects in whom a diagnosis of TB was excluded. Additional testing included sputum smear microscopy, sputum culture (solid and liquid media), mycobacterial blood culture, and urinary testing for LAM using a lateral flow test ('LF-LAM') and an enzyme-linked immunosorbance assay ('ELISA-LAM'). Among 103 participants with culture-confirmed TB, sensitivity of Xpert was 76% (95% confidence interval, CI 0.66-0.84), and was superior to that of LF-LAM (49%, 95% CI 0.39-0.59, P < 0.001). Specificity was greater than 97% for both tests among 105 individuals without TB. The combination of smear microscopy and LF-LAM identified 67% (95% CI 0.57-0.76) of culture-confirmed TB cases and approached sensitivity of Xpert testing alone (P = 0.15). The sensitivity of the combination of Xpert and LF-LAM was 85% (88/103 95% CI 0.77-0.92), which was superior to either test alone (P < 0.05) and approached sensitivity of sputum liquid culture testing (94%, 95% CI 0.88-0.98, P = 0.17). Sputum Xpert and urinary LAM assays were complementary for the diagnosis of active TB in HIV-infected patients, and sensitivity of the combination of these tests was superior to that of either test alone.

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.

Treatment response biomarkers are needed in the care of patients hospitalised with HIV-associated tuberculosis (TB). We describe the changes in bacillary load during early treatment using quantitative and semi-quantitative measures of Mycobacterium tuberculosis in blood and urine. We collected serial blood and urine samples at multiple timepoints in consenting adult patients with HIV and positive urine lipoarabinomannan (LAM), admitted to Mitchells Plain Hospital, Cape Town. Blood and urine Xpert Ultra, mycobacterial blood culture and urine LAM were performed. Survival analysis and mixed-effects modelling were used to determine time to a negative test, and to give the predicted probability of a positive test at the different timepoints. Sixteen participants, predominantly male (63%), with median age 39 years (interquartile range [IQR] 36-43), and CD4 count 27 cells/mm3 (IQR 8-83) were included. At day 14, urine LAM, urine Xpert Ultra and blood Xpert Ultra remained positive in between 75% and 86% of the participants. A mixed-effects model predicted a decline in ordinal values of urine Xpert Ultra (cycle threshold), blood Xpert Ultra (cycle threshold) and blood culture (time-to-positivity) in response to anti-TB treatment. Conversely, urine LAM grade intensity increased over the 14 days. M. tuberculosis DNA was detectable in urine and blood in decreasing quantity up to 14 days of standard treatment in patients with HIV-associated TB. Urine Alere LAM showed an increasing grade intensity during this period. Further research in larger groups and extended periods are needed to assess relation to clinical outcomes.

Smear-Negative Pulmonary Tuberculosis in Industrialized Countries

To evaluate the effectiveness of available rapid diagnostic tests to identify tuberculosis (TB) infection. Electronic databases were searched from 1975 to August 2003 for tests for active TB and to March 2004 for tests for latent tuberculosis infection (LTBI). Studies were selected and evaluated that (1) tested for LTBI, (2) compared tuberculin skin test (TST) and interferon-gamma assays based on ESAT-6 and CFP-10 antigens and (3) provided information on TB exposure or bacille Calmette-Guerin (BCG) vaccination or HIV status. For each test comparison, the sensitivity, specificity and 95% confidence intervals (CIs) were calculated. Sources of heterogeneity were investigated by adding covariates to the standard regression model. The authors examined whether interferon-gamma assays were more strongly associated with high versus low TB exposure than TST. Odds ratios (ORs) were calculated for the association between test results and exposures from each study along with their 95% CIs. Within each study, the OR value for one test was divided by that for another to produce a ratio of OR (ROR). A total of 212 studies were included, providing 368 data sets. A further 19 studies assessing fully automated liquid culture were included. Overall, nucleic acid amplification test (NAAT) accuracy was far superior when applied to respiratory samples as opposed to other body fluids. The better quality in-house studies, were, for pulmonary TB, much better at ruling out TB than the commercial tests (higher sensitivity), but were less good at ruling it in (lower specificity), but it is not possible to recommend any one over another owing to a lack of direct test comparisons. The specificity of NAAT tests was high when applied to body fluids, for example for TB meningitis and pleural TB, but sensitivity was poor, indicating that these tests cannot be used reliably to rule out TB. High specificity estimates suggest that NAAT tests should be the first-line test for ruling in TB meningitis, but that they need to be combined with the result of other tests in order to rule out disease. Evidence for NAAT tests in other forms of TB and for phage-based tests is significantly less prolific than for those above and further research is needed to establish accuracy. There is no evidence to support the use of adenosine deaminase (ADA) tests for diagnosis of pulmonary TB; however, there is considerable evidence to support their use for diagnosis of pleural TB and to a slightly lesser extent for TB meningitis. Anti-TB antibody test performance was universally poor, regardless of type of TB. Fully automated liquid culture methods were superior to culture on solid media, in terms of their speed and their precision. In total, 13 studies were included. Assays based on RD1 specific antigens, ESAT-6 or CFP-10, correlate better with intensity of exposure, and therefore are more likely than TST/purified protein derivative (PPD)-based assays to detect LTBI accurately. An additional advantage is that they are more likely to be independent of BCG vaccination status and HIV status. The NAAT tests provide a reliable way of increasing the specificity of diagnosis (ruling in disease) but sensitivity is too poor to rule out disease, especially in smear-negative (paucibacillary) disease where clinical diagnosis is equivocal and where the clinical need is greatest. For extra-pulmonary TB, clinical judgement has both poor sensitivity and specificity. For pleural TB and TB meningitis, adenosine deaminase tests have high sensitivity but limited specificity. NAATs have high specificity and could be used alongside ADA (or interferon-gamma) to increase sensitivity for ruling out disease and NAAT for high specificity to rule it in. All studies from low-prevalence countries strongly suggest that the RD1 antigen-based assays are more accurate than TST- and PPD-based assays for diagnosis of LTBI. If their superior diagnostic capability is found to hold up in routine clinical practice, they could confer several advantages on TB control programmes. Further research for active TB needs to establish diagnostic accuracy in a wide spectrum of patients, against an appropriate reference test, and avoiding the major sources of bias. For LTBI, research needs to address different epidemiological and clinical settings, to evaluate the performance of the main existing commercial assays in head-to-head comparison in both developed and developing countries, and to assess the role of adding more TB-specific antigens to try to improve diagnostic sensitivity.