A borderline range for Quantiferon Gold In-Tube results

Jerker Jonsson, Anna Westman, Judith Bruchfeld, Erik Sturegård, Hans Gaines and Thomas Schön

PLOS ONE, 2017, vol. 12, issue 11, 1-10

Abstract: Objective: Interferon gamma release assays like Quantiferon Gold In-Tube (QFT) are used to identify individuals infected with Mycobacterium tuberculosis. A dichotomous cut-off (0.35 IU/ml) defines a positive QFT without considering test variability. Our objective was to evaluate the introduction of a borderline range under routine conditions. Methods: Results of routine QFT samples from Sweden (2009–2014) were collected. A borderline range (0.20–0.99 IU/ml) was introduced in 2010 recommending a follow-up sample. The association between borderline results and incident active TB within 3 to 24 months was investigated through linkage with the national TB-register. Results: Using the recommended QFT cut-off, 75.1% tests were negative, 21.4% positive and 3.5% indeterminate. In total, 9% (3656/40773) were within the borderline range. In follow-up samples, individuals with initial results between 0.20–0.34 IU/ml and 0.35–0.99 IU/ml displayed negative results below the borderline range ( 0.99 IU/ml, 65 (0.97%) developed incident TB within 3–24 months. Conclusions: We recommend retesting of subjects with QFT results in the range 0.20–0.99 IU/ml to enhance reliability and validity of the test. Half of the subjects in the borderline range will be negative at a level

Date: 2017
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Persistent link: https://EconPapers.repec.org/RePEc:plo:pone00:0187313

DOI: 10.1371/journal.pone.0187313

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