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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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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
PLoS ONE
volume
12
issue
11
article number
e0187313
publisher
Public Library of Science (PLoS)
external identifiers
  • pmid:29095918
  • wos:000414340200071
  • scopus:85033400898
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
2025-01-08 00:57:59
@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>}},
  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 (PLoS)}},
  series       = {{PLoS ONE}},
  title        = {{A borderline range for Quantiferon Gold In-Tube results}},
  url          = {{http://dx.doi.org/10.1371/journal.pone.0187313}},
  doi          = {{10.1371/journal.pone.0187313}},
  volume       = {{12}},
  year         = {{2017}},
}