Background Inclusion of additional cytokine response may improve the diagnostic accuracy of Interferon-gamma releasing assay (IGRA) in highly tuberculosis (TB) endemic area. Objectives We aimed to compare cytokine profiles between pulmonary tuberculosis (PTB) patients and the healthy control and to improve IGRA by evaluating multiple cytokine response. Materials and Methods A hospital based cross sectional study was conducted in the Philippines. From December 2012 to February 2013, we recruited sputum smear-positive PTB patients (n=29), household contacts (n=8), health care workers (HCW) in TB department (n=21), and HCW in non-TB department (n=22). The level of eight cytokines (IFN-γ, IL-2, TNF-α, IL-4, IL-5, IL-10, IL-17A and IL-6) in their plasma were measured by Luminex TM assay after culture with ESAT-6, CFP-10 and TB7.7 in QuantiFERON TM -TB Gold In-Tube. Results IFN-γ/IL-2 ratio was significantly higher in PTB patients (median 2.06, interquartile range 1.30-4.20) than household contact (0.94 0.53-1.19, p=0.01), HCW in TB department (0.90 0.56-1.21, p=0.0004) and HCW in non-TB department (0.56 0.10-1.47, p=0.0094). In addition, IFN-γ/IL-2 ratio AUC (area under curve) =0.79 could distinguish PTB patients from household contacts more accurately than a IFN-γ response (AUC=0.50) based on receiver operating characteristic analysis (p=0.0009). Conclusions We found that IFN-γ/IL-2 ratio could distinguish PTB from healthy control more accurately than single cytokine detection. IGRA with additional cytokine detection provides useful information in a highly tuberculosis endemic country.
Sakashita et al. (Mon,) studied this question.