Characteristics of the study population
The present study included 28 HD patients with LTBI (HD/LTBI), 47 HD patients without LTBI (HD/normal) and 48 HCs (see Table 1). The average age was 62.0 ± 11.18 years for the HD/LTBI group, 60.70 ± 12.46 years for the HD/normal group, and 23.94 ± 2.72 years for the HC group. HD groups were older than the HC group; however, there were no difference between HD/LTBI and HD/normal groups. The male proportion of HD/LTBI group (18/28) was significantly higher than the HD/normal (16/47) and HC groups (21/48) (P = 0.038).
Previous TB contact and abnormal CXR lesion of the HD/LTBI groups was more frequent than the other two groups (P = 0.002 and P = 0.005, respectively); however, BCG vaccination or scar of HD/LTBI groups was less frequent than other two groups (P < 0.001). There was no significant difference in terms of underlying diseases like DM and IHD between HD/LTBI and HD/normal groups. Low BMI in HD/LTBI groups was significantly more frequent than in the HD/normal group (P = 0.012).
The amount of IFN-γ released after T-cell mitogen stimulation in QFT-GIT was analyzed in HD and HC groups (Table 1). There was statistically significant difference among the HD/LTBI, HD/normal, and HC groups (P = 0.005). In addition, the amounts of IFN-γ in the HD group were lower than in the HC group (P = 0.001).
QFT-GIT test results and previous QFT-GIT test results within 6 months
Most of the HD patients had repeated QFT-GIT test within 4 to 6 months. QFT-GIT test responses according to positive (> 0.7 IU/mL), borderline (0.2-0.7 IU/mL), and negative (< 0.2 IU/mL) criteria were as follows: Negative results were 97.9% in the HD/normal group, and positive results were 75% in the HD/LTBI group (see Table 2). Borderline results were 25% in the HD/LTBI group, 2.1% in the HD/normal group, and 4.2% in the HC group.
Previous QFT-GIT test response in HD patients was as follows: Positive results were 92.9% in the HD/LTBI group and 21.3% in the HD/normal group. Negative results were 3.6% in the HD/LTBI group and 51.5% in the HD/normal group. Borderline results were 3.6% in the HD/LTBI group and 27.7% in HD/normal group.
Based on the cut-off value of 0.35 IU/mL, conversion rate was 3.1% (1/32), and reversion rate was 37.2% (16/43). In addition, the reversion rate of the 0.35-0.7 IU/mL response group (85.7%, 6/7) was statistically higher than the > 0.7 IU/mL response group (27.8%, 10/36) (P = 0.0162). According to the three QFT-GIT test response groups, 92.7% (13/14) of previous 0.35-0.7 IU/mL response cases and 25% (9/36) of previous > 0.7 IU/mL response cases changed to negative results following QFT-GIT test (see Fig 1, P < 0.001).
Comparison of target gene mRNA expression levels after stimulation of MTB-specific Ags for 24 hours according to LTBI diagnosis
There were no statistically significant differences for mRNA expression levels of IFN-γ, TNF-α, IL-2R, CXCL9, CXCL11, IP-10, GM-CSF, and TNFR (Figure 1-a, b, c, d, e, f, h, i) among the three groups. However, there were statistically significant difference in only CCL11 mRNA expression levels (P = 0.028): mRNA expression level was higher in the HD/LTBI group (126.36 ± 406.25) than in the other two groups (HD/normal, 6.12 ± 17.45 vs HC, 19.58 ± 55.86, Figure 1-g). Within HD groups, the CCL11 of the HD/LTBI group was significantly higher than the HD/normal group (P = 0.0208).
Comparison of target gene mRNA expression levels after stimulation of MTB-specific antigens for 24 hours according to QFT-GIT response groups
There was no significant difference among three QFT-GIT response groups in terms of IFN- γ, TNF-α, IL-2R, CXCL9, CXCL11, and IP-10 (figure 2-a, b, c, d, e, f). However, CCL11 mRNA expression levels in the > 0.7 IU/mL response group (168 ± 464) was significantly higher than in the < 0.2 IU/mL response group (13.1 ± 42.5) and 0.2 to 0.7 IU/mL response group (2.55 ± 6.43, P = 0.0043, Figure 2-g). Compared to CCL11 mRNA expression level, GM-CSF mRNA expression levels in the 0.2 to 0.7 IU/mL response group (1,512,106 ± 4,781,492) were significantly higher than the < 0.2 IU/mL response group (626 ± 4129) and > 0.7 IU/mL response group (15 ± 53.9, P = 0.0029, Figure 2-h). TNFR mRNA expression levels in the < 0.2 IU/mL response group (227,937 ± 720,687) were significantly higher than the QFT-GIT-1 group (2.31 ± 4.44) and > 0.7 IU/mL response group (4.01 ± 8.81, P=0.0029, Figure 2-i). Although there was no significant difference (P = 0.0981), mRNA expression level of IL-2R in the > 0.7 IU/mL response group was higher than in the less than 0.7 IU/mL groups (Figure 2-c).
Comparison of Target gene mRNA expression levels after stimulation of MTB-specific antigens for 24 hours according to QFT-GIT response groups in HD
There was statistically significant difference in mRNA expression of CCL11 among QFT-GIT test response groups in HD patients (P = 0.041), for which the expression levels in the > 0.7 IU/mL response group was higher than that of the other two groups (Figure 3-g).
The mRNA expressions of GM-CSF and TNFR differed significantly (P = 0.0132), and the expression levels of the 0.2 to 0.7 IU/mL response group was higher than the other two groups compared to CCL11 (Figure 3- h, Figure 3-i). The mean value of TNFR mRNA expression in the 0.2 to 0.7 IU/mL response group was higher than the other two groups; however, the median value of TNFR mRNA expression in the > 0.7 IU/mL response group was higher than in the other two groups. If one case with extreme values of GM-CSF and TNFR mRNA expression among the 0.2 to 0.7 IU/mL response group was excluded, there were no statistical differences for GM-CSF and TNFR mRNA expression among the three QFT-GIT test response groups. However, there were significant differences of GM-CSF and TNFR mRNA expression between the < 0.2 IU/mL response group and 0.2 to 0.7 IU/mL response group (P = 0.0083). There was no significant difference among three QFT-GIT response groups in terms of IFN- γ, TNF-α, IL-2R, CXCL9, CXCL11, and IP-10 (Figure 3-a, b, c, d, e, f).
Comparison of clinical features, and mRNA expression of cytokine and chemokine between IGRA reversion and persistent group in HD group
There were no statistically significant differences between the reversion group (n = 16) and the persistent group (n = 58) in terms of sex, age, DM, IHD, plasma IFN-γ protein level after T-cell mitogen stimulation and LTBI treatment. Also, there was no statistically significant differences in terms of cytokines and chemokines.