Abstract
We investigated changes in the interferon-γ levels before and after treatment of latent tuberculosis infection (LTBI) using QuantiFERON-TB Gold Plus (QFT-Plus) and QuantiFERON-TB Gold In-Tube (QFT-GIT) assays. The objective was to assess whether QFT-Plus could serve as a biomarker of LTBI treatment response. We prospectively enrolled 44 individuals whose baseline QFT-GIT and QFT-Plus showed positive results at a tertiary referral center in South Korea between March 2017 and March 2018. The results of the QFT-Plus assay were defined as positive if either or both of the antigen tubes (TB1 and/or TB2) were positive. After LTBI treatment, both tests were repeated. The mean age of the participants was 47.6 years. The QFT-GIT and QFT-Plus assays revealed positive results in 42/44 (95.5%) and 41/44 (93.2%) participants after LTBI treatment, showing overall agreement of 93.2%, with a Cohen's kappa value of 0.37 (fair agreement). The differences between pre- and post-LTBI treatment interferon-γ levels were measured using the QFT-GIT and QFT-Plus assays. No significant differences were noted among the 3 values: the median difference in interferon-γ value with QFT-GIT, QFT-Plus TB1, and QFT-Plus TB2 was 0.211 IU/mL (IQR, -0.337-3.347), 0.025 IU/mL (IQR, -0.338-1.368), and 0.180 IU/mL (IQR, -0.490-2.278), respectively (P = 0.401). The change in interferon-γ levels before and after LTBI treatment measured using the QFT-Plus assay showed a similar trend to that of the QFT-GIT assay. Considering that the QFT-GIT assay is not a useful biomarker of LTBI treatment response, QFT-Plus also appears not to be useful for this purpose.
Highlights
Latent tuberculosis infection (LTBI) is defined as a state wherein humans are infected with Mycobacterium tuberculosis without any clinical symptoms, radiological abnormality, or microbiological evidence of infection [1,2]
No significant differences were noted among the 3 values: the median difference in interferon-γ value with QuantiFERONTB Gold In-Tube (QFT-GIT), QFT-Plus tube 1 (TB1), and QFT-Plus tube 2 (TB2) was 0.211 IU/mL (IQR, −0.337–3.347), 0.025 IU/mL (IQR, −0.338– 1.368), and 0.180 IU/mL (IQR, −0.490–2.278), respectively (P = 0.401)
We enrolled 44 participants whose baseline QFT-GIT and QFT-Plus assay showed positive results and who received repeat tests of the QFT-GIT and QFT-Plus assay after latent tuberculosis infection (LTBI) treatment (Fig 1)
Summary
Latent tuberculosis infection (LTBI) is defined as a state wherein humans are infected with Mycobacterium tuberculosis without any clinical symptoms, radiological abnormality, or microbiological evidence of infection [1,2]. The World Health Organization guidelines recommend the use of a tuberculin skin test or interferon-γ release assay (IGRA) for detection of LTBI in high-income and upper middleincome countries that have an estimated TB incidence of
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