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Despite efforts to improve tuberculosis (TB) detection, limitations in access, quality and timeliness of diagnostic services in low- and middle-income countries are challenging for current TB diagnostics. This study aimed to identify and characterise a metabolic profile of TB in urine by high-field nuclear magnetic resonance (NMR) spectrometry and assess whether the TB metabolic profile is also detected by a low-field benchtop NMR spectrometer. We included 189 patients with tuberculosis, 42 patients with pneumococcal pneumonia, 61 individuals infected with latent tuberculosis and 40 uninfected individuals. We acquired the urine spectra from high and low-field NMR. We characterised a TB metabolic fingerprint from the Principal Component Analysis. We developed a classification model from the Partial Least Squares-Discriminant Analysis and evaluated its performance. We identified a metabolic fingerprint of 31 chemical shift regions assigned to eight metabolites (aminoadipic acid, citrate, creatine, creatinine, glucose, mannitol, phenylalanine, and hippurate). The model developed using low-field NMR urine spectra correctly classified 87.32%, 85.21% and 100% of the TB patients compared to pneumococcal pneumonia patients, LTBI and uninfected individuals, respectively. The model validation correctly classified 84.10% of the TB patients. We have identified and characterised a metabolic profile of TB in urine from a high-field NMR spectrometer and have also detected it using a low-field benchtop NMR spectrometer. The models developed from the metabolic profile of TB identified by both NMR technologies were able to discriminate TB patients from the rest of the study groups and the results were not influenced by anti-TB treatment or TB location. This provides a new approach in the search for possible biomarkers for the diagnosis of TB.

The objective was to assess the annual risk of tuberculosis infection by means of tuberculin skin testing (TST) in children, evaluating whether QuantiFERON-TB Gold In-Tube (QFN-G-IT) could improve the accuracy. On the basis of the positive TST results, the global annual incidence was estimated at 0.78%, with an increase in the prevalence from 0.64% to 1.68% in 2 years. However, QFN-G-IT was only positive in 6 of the 25 children with positive TST. The confirmation of the positive TST results by QFN-G-IT provided more accurate annual incidence estimation.

Resumen Las terapias biologicas basadas en antagonistas del factor de necrosis tumoral alfa (TNF-α) han aparecido como una opcion terapeutica eficaz en las enfermedades inflamatorias cronicas. Sin embargo, dado que existe una asociacion entre tratamiento con anti-TNF-α y reactivacion de la infeccion tuberculosa, se requiere una evaluacion previa del paciente para evitar progresion a enfermedad tuberculosa en caso de estar infectado. La tuberculina se utiliza para el diagnostico de la infeccion tuberculosa, pero presenta una baja especificidad en pacientes vacunados con el bacilo de Calmette-Guerin (BCG) y una baja sensibilidad en pacientes con alteraciones de la inmunidad celular. En los ultimos anos se han desarrollado diferentes metodologias in vitro que utilizan antigenos especificos de Mycobacterium tuberculosis para estimular las celulas T sensibilizadas y detectar posteriormente el interferon-γ liberado para el diagnostico in vitro de la infeccion tuberculosa. Los resultados obtenidos hasta ahora muestran a estas como una alternativa real a la tuberculina, ya que presentan una mayor especificidad y sensibilidad. A pesar de que existen algunos resultados preliminares que apuntan a que podamos plantear la utilizacion unica de las tecnicas in vitro, lo mas prudente seria utilizarlas en combinacion con la tuberculina, considerando infeccion cuando cualquiera de las 2 tecnicas sea positiva.

The aim of our work here was to evaluate the immunogenicity of 60 mycobacterial antigens, some of which have not been previously assessed, notably a novel series of in vivo-expressed Mycobacterium tuberculosis (IVE-TB) antigens. We enrolled 505 subjects and separated them in individuals with and without latent tuberculosis infection (LTBI) vs. patients with active tuberculosis (TB). Following an overnight and 7 days stimulation of whole blood with purified recombinant M. tuberculosis antigens, interferon-γ (IFN-γ) levels were determined by ELISA. Several antigens could statistically significantly differentiate the groups of individuals. We obtained promising antigens from all studied antigen groups [dormancy survival regulon (DosR regulon) encoded antigens; resuscitation-promoting factors (Rpf) antigens; IVE-TB antigens; reactivation associated antigens]. Rv1733, which is a probable conserved transmembrane protein encoded in DosR regulon, turned out to be very immunogenic and able to discriminate between the three defined TB status, thus considered a candidate biomarker. Rv2389 and Rv2435n, belonging to Rpf family and IVE-TB group of antigens, respectively, also stood out as LTBI biomarkers. Although more studies are needed to support our findings, the combined use of these antigens would be an interesting approach to TB immunodiagnosis candidates.

Summary Objective Performance of IFN-γ assays in children is compromised. Therefore, we investigated the utility of IP-10 for the detection of active tuberculosis (TB) and latent tuberculosis infection (LTBI) diagnosis in children; comparing its positivity with QuantiFERON-TB Gold In-Tube (QFN-G-IT) and T-SPOT.TB. Methods We studied 230 children from three groups: active TB, screening (healthy children without known exposure to active TB patient screened at school or by their paediatrician) and contact-tracing studies. IFN-γ release was determined by QFN-G-IT and T-SPOT.TB. IP-10 was detected in QFN-G-IT supernatants by ELISA. Results When combining QFN-G-IT and IP-10 assays, positive results improved significantly from 38.3% in QFN-G-IT and 33.9% in IP-10 to 41.3%. Age and type of contact were significant risk factors associated with positive QFN-G-IT and IP-10 results. IP-10 levels after antigen-specific stimulation were significantly higher in comparison to IFN-γ levels. Correlation between the three assays was good ( κ = 0.717–0.783). Conclusions IP-10 cytokine is expressed in response to TB specific-antigens used in QFN-G-IT. In conclusion, the use of IFN-γ T-cell based assays in combination with an additional IP-10 assay detection could be useful for diagnosing active TB and LTBI in children.