Comparison of whole-blood interferon-γ assay and flow cytometry for the detection of tuberculosis infection

Abstract

Objective: Limited data exist about the performance of the intracellular cytokine flow cytometry (ICCFC) with respect to that of the commercial interferon-γ release assay for the detection of tuberculosis (TB) infection. Here, we compared the diagnostic accuracy of an ICCFC with that of the QuantiFERON-TB Gold In-Tube (QFT-IT) test for the detection of TB in a clinical setting.

Methods: Eighty-nine patients suspected of having TB were prospectively included. Both the QFT-IT test and ICCFC were performed for all subjects (TB [n = 65] and non-TB [n = 24]). Ten healthy controls who tested negative by QFT-IT were also assessed by ICCFC.

Results: The sensitivity of the ICCFC was significantly superior to that of the QFT-IT test (91% vs. 78%, p = 0.021). The clinical characteristics of patients in whom the ICCFC exhibited superior sensitivity compared to the QFT-IT test included advanced age, lymphocytopenia, hypoalbuminemia, increased C-reactive protein level, a positive acid-fast bacilli smear of respiratory specimens, and radiographically more extensive disease.

Conclusions: ICCFC might be a preferable technique for the detection of TB infection, particularly in patients with conditions associated with impaired performance of the QFT-IT test.