Comparison of interferon-gamma production between TB1 and TB2 tubes of QuantiFERON-TB Gold Plus: a meta-analysis

CD8+ T cell response in QuantiFERON-TB Gold Plus testing was associated with tuberculosis recurrence: a 2-year prospective study

BACKGROUND

Recurrence posed an important challenge to pulmonary tuberculosis (PTB) control in China. The prospective study aimed to identify potential risk factors and to explore the value of QuantiFERON-TB Gold Plus (QFT-Plus) in identifying at-risk individuals with treated prior PTB history.

METHODS

All eligible individuals aged ≥18 years who had been diagnosed with PTB before 2016 in Zhongmu County, where with an average level of TB prevalence in China, were included and received baseline survey including chest radiography, QuantiFERON-TB Gold In-Tube (QFT-GIT) and QFT-Plus, then PTB recurrence was tracked through a 2-year follow-up.

RESULTS

Half of 1068 (52.34%, 559/1068) included eligible participants were QFT-Plus positive at baseline and 21 of them recurred active TB in 2-year follow-up. Individuals aged ≥ 60 years, who had a recent history of TB and smokers were associated with increased risk of TB recurrence with an adjusted odds ratio (aOR) of 3.97 (95% confidence interval (CI): 1.29-12.24), 7.71 (95% CI: 1.74-34.25) and 4.56 (95% CI: 1.62-12.83), respectively. Compared to QFT-Plus negatives, those who were TB2+/TB1- (aOR = 15.34) exhibited stronger association with the risk of TB recurrence than those who were TB1+/TB2+ (aOR = 6.06). A dose response relationship was also found between the risk of TB recurrence with the baseline level of TB2-TB1 (p for trend < 0.001).

CONCLUSIONS

High burden of TB infection and high risk of PTB recurrence were observed in the study population. Those with recent onset of prior TB, elderly smokers and QFT-Plus positives especially with TB2 single positive deserved further attention in active TB surveillance.

Predicting stringent QuantiFERON-TB Gold Plus conversions in contacts of tuberculosis patients

OBJECTIVES

To assess associations between disease severity in index TB patients and QuantiFERON-TB Gold Plus (QFT-Plus) results in contacts, and predictors for QFT-Plus conversion in contacts over 6-12 months.

METHODS

TB patients (n = 295) and the contacts (n = 1051) were enrolled during 2018-2021 with QFT-Plus performed at baseline and months 6 and 12. A strong CD8 response was defined as TB2 interferon gamma (IFN-γ) response minus TB1 >0.6 IU/ml and stringent conversion as change from QFT-plus negative to high-positive QFT-Plus (TB1 or TB2 IFN-γ responses >0.7 IU/ml).

RESULTS

Contacts with index TB patients with sputum smear >1+ was associated with positive QFT-Plus compared to those without (p < 0.001). Contacts with index TB patients with bilateral lung disease were more likely to have strong CD8 responses than those without (p = 0.038). QFT-Plus stringent conversion occurred in 9.7% of contacts over 6-12 months. A TB1 IFN-γ response ≥0.03 IU/ml combined with a TB2 ≥0.06 IU/ml was predictive of a 19-fold increased risk for QFT-Plus stringent conversion in contacts (odd ratio 19.565 [8.484-45.116], p < 0.001).

CONCLUSION

Bacterial burden and bilateral lung disease of index TB patients were associated with positive QFT-Plus and strong CD8 responses in contacts. TB1 and TB2 IFN-γ responses were synergistically predictive of stringent conversion in contacts.