Abstract: Objective  To evaluate the clinical influencing factors on the whole blood gamma release assay in the patients with pulmonary tuberculosis.  Methods  One hundred and six clinical diagnosed tuberculosis patients who included 44 smear- or culture-positive cases，47 smear- or culture-negative cases and 15 cases with non-active pulmonary tuberculosis and 35 healthy controls were enrolled in this study. The heparinized bloods from all participants were incubated with purified protein derivative (PPD) and M. tuberculosis-specific antigens early secretory antigen target 6 (ESAT-6) and ESAT-6/CFP-10 fusion protein encoded in the mycobacterial genomic region of difference (RD1). The production of interferon γ (IFN-γ) was detected with ELISA.  Results  There were no significant difference between smear-positive group and smear-negative group in the IFN-γ median stimulated by ESAT-6 (114.7 pg/ml vs 82 pg/ml, Z=－0.500, P>0.05), ESAT-6/CFP-10 (3488 pg/ml vs 2350 pg/ml, Z=－0.949, P>0.05) and PPD (4514 pg/ml vs 4326 pg/ml, Z=－0.822, P>0.05). The IFN-γ median stimulated by ESAT-6 (82 pg/ml vs 137 pg/ml, Z=－0.781, P>0.05) and ESAT-6/CFP-10 (2350 pg/ml vs 1784 pg/ml, Z=－1.685, P>0.05) had not significant difference between the smear-negtive pulmonary tuberculosis group and non-active pulmonary tuberculosis group. However, there were statistic difference between smear-positive pulmonary tuberculosis group and non-active pulmonary tuberculosis group in the IFN-γ median stimulated by ESAT-6/CFP-10（3488 pg/ml vs 1784 pg/ml, Z=－0.242, P<0.05). The patients with less than 4 segments of lesions on the X-ray had higher IFN-γ median than those with more than 4 segments of lesions ［ESAT-6 (117 pg/ml vs 42 pg/ml, Z=－2.341, P<0.05), ESAT-6/CFP-10 (3055 pg/ml vs 1562.5 pg/ml, Z=－2.850, P<0.05)］. There were also significant difference between the patients with higher peripheral blood lymphocyte count (≥1.0×10⁹/L) and those with lower peripheral blood lymphocyte count (<1.0×10⁹/L) in the IFN-γ median ［ESAT-6 (97.5 pg/ml vs 48 pg/ml, Z=－2.745, P<0.05), ESAT-6/CFP-10（3082 pg/ml vs 1190 pg/ml, Z=－2.911, P<0.05），PPD（4322 pg/ml vs 3200 pg/ml, Z=－2.216, P<0.05）］.  Conclusion The production of IFN-γ stimulated by M. tuberculosis-specific antigens was not influenced by the load of bacilli, and probably influenced by accumulated lesion in X-ray and peripheral blood lymphocyte count.

Key words: Tuberculosis, pulmonary/diagnosis, Interferon-gamma release tests