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Title

Indeterminate test results of T-SPOT.TB performed under routine field conditions

Authors
Beffa, P.
Zellweger, A.
Wrighton-Smith, P.
Zellweger, J-P.
Published in The European respiratory journal. 2008, vol. 31, no. 4, p. 842-6
Abstract Interferon-gamma release assays for the diagnosis of tuberculosis (TB) can give indeterminate results. The prevalence of indeterminate test results (ITRs) among T-SPOT.TB tests was assessed. A retrospective analysis of samples processed in 2005 was performed. ITRs were assessed by age, sex, immunosuppression, distance to the laboratory and season. A subgroup of tests performed for specific indications (contact tracing, migrants with positive tuberculin skin test, TB suspects and immunosuppression) were analysed separately. Of a total of 1,429 tests, 49 (3.4%) were indeterminate. ITRs were significantly associated with old age (>75 versus 5-75 yrs; odds ratio (OR) 7.97, 95% confidence interval (CI) 3.968-15.438) and the season during which samples were transported (autumn and winter versus spring and summer; OR 3.47, 95% CI 1.753-7.514). The incidence of ITR was 302 (2.0%) among TB contacts, 75 (1.6%) among immigrants, 156 (3.0%) in TB suspects and 32 (3.0%) among immunosuppressed patients. Sex, young age and distance to the laboratory were not associated with the rate of ITR. Of the 13 tests with ITR that were repeated, 10 gave a clear positive or negative result. Indeterminate test results with T-SPOT.TB under routine conditions were infrequent and more common in individuals aged >75 yrs than in children and younger adults. The incidence of indeterminate test results was low and similar among healthy tuberculosis contacts, immigrants with a positive tuberculin skin test, tuberculosis suspects and the immunosuppressed. The conditions of transportation may influence the incidence of indeterminate test results.
Keywords AdolescentAdultAge FactorsAgedAged, 80 and overChildChild, PreschoolFemaleHumansInfantInterferon-gamma/analysis/metabolismMaleMass Screening/methodsMiddle AgedReagent Kits, Diagnostic/microbiologyRetrospective StudiesSensitivity and SpecificityT-Lymphocytes/metabolism/microbiologyTuberculosis/blood/diagnosis
Identifiers
PMID: 18057053
Note Republished in: Pneumologia. 2008 Apr-Jun;57(2):109-13.
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Other version: http://erj.ersjournals.com/cgi/content/full/31/4/842
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BEFFA, P. et al. Indeterminate test results of T-SPOT.TB performed under routine field conditions. In: European respiratory journal, 2008, vol. 31, n° 4, p. 842-6. https://archive-ouverte.unige.ch/unige:2418

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Deposited on : 2009-08-12

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