From symptoms to diagnosis of Urban Tuberculosis, considering individual and contextual factors. What are the determinants and critical points of this delay?s pathway?

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Tuberculin skin test and interferon‐γ release assays: Can they agree?

Publication . Santos, João Almeida; Duarte, Raquel; Nunes, Carla

Introduction: The diagnosis of latent tuberculosis infection (LTBI) relies largely on the tuberculin skin test (TST) or, more recently, on interferon-gamma release assays (IGRA). Knowledge regarding these tests is essential to improve their usefulness in combating the tuberculosis epidemic. Objectives: To characterize the agreement between the IGRA and TST tests by determining the kappa coefficient (K) and agreement rate between these two tests in patients with active tuberculosis (TB). Methods: Retrospective cohort study conducted with data from active TB patients notified in the Portuguese Tuberculosis Surveillance System (SVIG-TB), from 2008 to 2015. TST results were interpreted using a 5 mm (TST-5 mm) and 10 mm (TST-10 mm) cutoff. Kappa coefficient and agreement rate were calculated in order to evaluate the agreement between IGRA and TST (both cutoffs) test results. Results: A total of 727 patients with results for both tests were included in the study, of which 3.4% (n = 25) had HIV infection, 5.6% (n = 41) diabetes, 5.0% (n = 36) oncological diseases and 4.4% (n = 32) inflammatory diseases. Of the 727 patients, 16.5% (n = 120) presented different outcomes between IGRA and TST-5 mm, and 20.5% (n = 149) presented different outcomes between IGRA and TST-10 mm. Kappa coefficient between IGRA and TST-5 mm was 0.402 (p < 0.001) with an agreement rate of 83.5%. Between IGRA and TST-10 mm, the kappa coefficient was 0.351 (p < 0.001), with an agreement rate of 79.5%. Patients with HIV infection, diabetes, oncologic diseases and inflammatory diseases presented a substantial agreement between IGRA and TST-5 mm, while inflammatory diseases was the only variable that presented a substantial agreement between IGRA and TST-10 mm. Conclusion: As both tests can present false-negative results, the low level of agreement between the tests can potentially help identify more cases of LTBI if the two tests are used in parallel, with infections not detected by IGRA possibly being detected by the TST and vice versa.

2022-12-16Journal article

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The effect of TB patient delay on loss to follow-up in Portugal

Publication . Marques, J.; Rocha, J.V.; Soares, Patricia; Leite, Andreia; Duarte, R.; Nunes, C.

BACKGROUND: Early identification of TB cases, followed by treatment to completion, are essential for controlling and preventing the disease. Previous studies have found some factors associated with both loss to follow-up (LTFU) and patient delay. We aim to build a causal model to investigate the association between TB patient delay and LTFU.METHODS: Pulmonary TB cases were identified using the national surveillance system in Portugal between 2008 and 2017. A directed acyclic graph was used to identify the minimal set of variables to adjust for when studying the association between delay (exposure) and LTFU (outcome). Crude and adjusted hazard were estimated using Cox regression.RESULTS: Nearly 4% of the patients did not follow up treatment. There was no association between patient delay and LTFU, even after adjustment with the minimal set of covariates. Factors associated with a higher risk of LTFU were being younger, being unemployed, living in urban areas, having HIV and the abuse of alcohol and drugs.CONCLUSION: Patient delay was not associated with LTFU, while social conditions were. Future research should investigate the underlying reasons why patients discontinue TB treatment and use these findings to develop targeted interventions that can support patients in completing their treatment regimen.

2023-07-01Journal article

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Host factors associated to false negative and indeterminate results in an interferon‐γ release assay in patients with active tuberculosis

Publication . Santos, J.A.; Duarte, R.; Nunes, C.

Information on host factors that contribute to false negative and indeterminate results in interferon-γ release assays (IGRA) are critical to improve the usefulness of these tests in the fight against tuberculosis (TB) epidemics. The aim of this study was to estimate and compare the sensitivity of an IGRA and the tuberculin skin test (TST), independently and as a combined approach, in patients with TB and to identify risk factors associated with false negative and indeterminate IGRA results.

2020-12-13Journal article

Open access