Association of the level of IFN-γ produced by T cells in response to Mycobacterium tuberculosis-specific antigens with the size of skin test indurations among individuals with latent tuberculosis in a highly tuberculosis-endemic setting.
There is growing evidence showing the potential of T-cell-based gamma interferon (IFN-γ) release assays (IGRAs) for predicting the risk of progression of Mycobacterium tuberculosis (Mtb) infection, though there is little information from tuberculosis (TB)-endemic settings. In this study, we assessed the association between the level of IFN-γ produced by T cells in response to Mtb-specific antigens and the size of skin test indurations in 505 adult individuals who were screened for latent tuberculosis infection (LTBI) using the QuantiFERON-TB Gold In Tube (QFTGIT) assay and tuberculin skin test (TST). There was a strong positive correlation between the level of IFN-γ induced by the specific antigens and the diameter of the skin indurations (Spearman's rho = 0.6, P < 0.001). Body mass index and parasitic infection were not associated with the level of IFN-γ production or the TST reaction. In linear regression analysis, the size of the skin test indurations was significantly associated with the mean level of IFN-γ [coefficient, 0.65; 95% confidence interval (CI), 0.47 to 0.82, P < 0.001]. Similarly, results from logistic regression analysis demonstrated that individuals who had skin test indurations ≥ 10 mm were 6.82 times more likely than individuals who had skin test indurations < 10 mm to have high levels of IFN-γ (i.e. positive QFTGIT result) (adjusted odd ratio = 6.82; 95% CI, 3.67 to 12.69, P < 0.001). In conclusion, the results of this study could provide indirect evidence for the prognostic use of the QFTGIT assay for progression of Mtb infection, though prospective follow-up studies are needed to provide direct evidence.
Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia. dlegessem@yahoo.com
Mengistu
M
Legesse
Gobena
G
Ameni
Gezahegne
G
Mamo
Girmay
G
Medhin
Gunnar
G
Bjune
Fekadu
F
Abebe
D000293:Adolescent; D000328:Adult; D000942:Antigens, Bacterial / Q000276:immunology*; D002478:Cells, Cultured; D018450:Disease Progression; D019353:Endemic Diseases; D005002:Ethiopia; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology*; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D011237:Predictive Value of Tests; D011379:Prognosis; D012306:Risk; D012882:Skin Tests; D013601:T-Lymphocytes / Q000276:immunology* / Q000382:microbiology; D055815:Young Adult
D000942:Antigens, Bacterial; D007371:Interferon-gamma