Evaluation of the QuantiFERON?-TB Gold In-Tube assay and tuberculin skin test for the diagnosis of Mycobacterium tuberculosis infection in northeastern Thailand.
BACKGROUND
The diagnosis of latent Mycobacterium tuberculosis infection (LTBI) is currently based on the immunological response of T-cells to M. tuberculosis (MTB) antigens. However, the QuantiFERON®-TB Gold In-Tube assay (QFT) has not yet been evaluated in the Thai adult population.


OBJECTIVE
To evaluate the diagnostic performance and determine predictors of discordant results between the QFT and tuberculin skin test (TST).


METHODS
Active tuberculosis (ATB) patients (n=54), close contacts (CCs) living in the same household as a TB patient (n=100) and healthy controls (HCs) (n=60) were interviewed and underwent the QFT and TST at Srinagarind Hospital in Thailand. Various cut-off values for the QFT (0.25-0.35 IU/mL) and TST (5-15 mm) were applied.


RESULTS
The maximum agreement rate between the tests was 71.5% (κ=0.41) with cut-offs of 0.35 IU/mL and 10 mm or 0.25 IU/mL and 10 mm. Based on standard cut-off values (0.35 IU/mL and 10 mm) and using ATB patients and HCs as positive and negative controls, the TST was more sensitive than the QFT (87.0% vs. 66.7%, respectively), whereas the QFT was more specific than the TST (83.3% vs. 70.0%, respectively). Being underweight (OR 3.86, 95%CI 1.3-11.48) or overweight (OR 5.9, 95%CI 1.24-28.16) was significantly associated with TST+/QFT- results. Diabetes (OR 32.56, 95%CI 1.73-613.49) and poor or fair nutrition (OR 7.4, 95%CI 1.23-44.57) were significantly associated with TST-/QFT+ results.


CONCLUSIONS
The TST should be used as a screening test based on its higher sensitivity, whereas the QFT should be used as a confirmatory test because of its higher specificity.
Department of Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
Wipa
W
Reechaipichitkul
Wilailuk
W
Pimrin
Janpen
J
Bourpoern
Supapim
S
Prompinij
Kiatichai
K
Faksri
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D002648:Child; D005260:Female; D054884:Host-Pathogen Interactions; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology*; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000276:immunology / Q000382:microbiology; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D013601:T-Lymphocytes / Q000276:immunology* / Q000382:microbiology; D013785:Thailand; D014374:Tuberculin Test; D055815:Young Adult
C573415:IFNG protein, human; D007371:Interferon-gamma