Combination of serological and cytokine release assays for improved diagnosis of childhood tuberculosis in Zambia (PROMISE-TB)

Abstract

Objectives: The diagnostic gaps for childhood tuberculosis (TB) remain considerable in settings with high TB incidence and resource constraints. We established and evaluated the performance of a scoring system based on a combination of serological tests and T-cell cytokine release assays, chosen for their ability to detect immune responses indicative of TB, in a context of high prevalence of pediatric HIV infection. Methods: We enrolled 628 consecutive children aged ≤15 years, admitted for TB suspicion. Multiple cytokine levels in QuantiFERON Gold In-Tube supernatants and antigen 85B (Ag85B) antibodies were assessed in children who tested positive with either Xpert TB or mycobacterial culture. The results were compared with those of control children. Results: Among the biomarkers most strongly associated with TB, random forest classification analysis selected Ag85B antibodies, interleukin-2/interferon-γ ratio, and monokine induced by interferon-γ for the scoring system. The receiver operating characteristic curve derived from our scoring system showed an area under the curve of 0.95 (0.91-0.99), yielding 91% sensitivity and 88% specificity. The internal bootstrap validation gave the following 95% confidence intervals for the score performance: sensitivity 71%-97% and specificity 79%-99%. Conclusions: This study suggests that supplementing the QuantiFERON assay with a combination of serological and T-cell markers could enhance childhood TB screening regardless of HIV status and age. Further validation among the target population is necessary to confirm the performance of this scoring system.

Keywords

• Tuberculosis
• IFN-gamma release assay (IGRA)
• Africa
• Children
• HIV