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A borderline range for Quantiferon Gold In-Tube results

Jonsson, Jerker; Westman, Anna; Bruchfeld, Judith; Sturegård, Erik LU ; Gaines, Hans and Schön, Thomas (2017) In PLoS ONE 12(11).
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.... (More)

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 (<0.20 IU/ml) in 66.1% (230/348) and 42.5% (285/671) respectively, and none developed incident TB. Among 6712 individuals with a positive initial test >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 <0.20 IU/ml when retested and have a very low risk of developing incident active TB.

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Contribution to journal
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published
subject
in
PLoS ONE
volume
12
issue
11
publisher
Public Library of Science
external identifiers
  • scopus:85033400898
  • wos:000414340200071
ISSN
1932-6203
DOI
10.1371/journal.pone.0187313
language
English
LU publication?
yes
id
facb2bab-685e-474f-b8c4-795609d48781
date added to LUP
2017-11-21 07:38:49
date last changed
2018-01-16 13:26:03
@article{facb2bab-685e-474f-b8c4-795609d48781,
  abstract     = {<p>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 (&lt;0.20 IU/ml)      in      66.1% (230/348) and 42.5% (285/671) respectively, and none developed incident      TB.      Among 6712 individuals with a positive initial test &gt;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      &lt;0.20      IU/ml when retested and have a very low risk of developing incident active      TB.</p>},
  articleno    = {e0187313},
  author       = {Jonsson, Jerker and Westman, Anna and Bruchfeld, Judith and Sturegård, Erik and Gaines, Hans and Schön, Thomas},
  issn         = {1932-6203},
  language     = {eng},
  month        = {11},
  number       = {11},
  publisher    = {Public Library of Science},
  series       = {PLoS ONE},
  title        = {A borderline range for Quantiferon Gold In-Tube results},
  url          = {http://dx.doi.org/10.1371/journal.pone.0187313},
  volume       = {12},
  year         = {2017},
}