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

Abstract

Abstract 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 6e12 months. Methods: TB patients (n Z 295) and the contacts (n Z 1051) were enrolled during 2018e2021 with QFT-Plus performed at baseline and months 6 and 12. A strong CD8 response was defined as TB2 interferon gamma (IFN-g) 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-g responses >0.7 IU/ml). Results: Contacts with index TB patients with sputum smear >1þ 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 Z 0.038). QFT-Plus stringent conversion occurred in 9.7% of contacts over 6e12 months. A TB1 IFN-g 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 [8.484e45.116], 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-g responses were synergistically predictive of stringent conversion in contacts.