The three-gene Xpert Host Response signature for pediatric tuberculosis screening: A prospective diagnostic accuracy study

Abstract

Background: Blood-based gene signatures offer potential as a near point-of-care tuberculosis (TB) screening tool. We examined the accuracy of the GeneXpert MTB Host Response (Xpert-HR) cartridge to screen for TB in children.

Methods: We enrolled children under 15 years from The Gambia and Uganda being evaluated for pulmonary TB. Each child provided a blood sample for Xpert-HR and underwent standard TB assessments, including chest x-ray (CXR) and sputum Xpert Ultra testing, followed by NIH case classification of Confirmed, Unconfirmed or Unlikely TB. We measured cycle threshold (Ct) values for GBP5, DUSP3, and TBP, calculated an HR TB score, and generated ROC curves. Specificity was assessed at 90% sensitivity according to strict (SRS, Confirmed versus Unlikely TB), microbiological (MRS, Confirmed versus Unlikely or Unconfirmed TB), and composite (CRS, Confirmed or Unconfirmed TB versus Unlikely TB) reference standards compared to other TB evaluations.

Results: Among 181 children (median age 4 years; 53% female; 16% with HIV; 14.4% confirmed TB), the HR TB score cut-point of -0.65 showed 88.5% sensitivity with specificity at 33.3% (SRS) and 30.3% (MRS). Sensitivity was lower for the CRS at 75.7%, with similar specificity (33.3%). Sensitivity was higher in children aged 5-9 and 10-14 years compared to those under 5, but specificity remained low (22.7-28.6%). Combining Xpert-HR with CXR, Xpert Ultra, or TB treatment decision algorithms did not significantly enhance accuracy.

Conclusion: Xpert-HR showed high sensitivity for detecting confirmed TB but had low specificity, risking overdiagnosis. Improved pediatric-specific gene signatures are necessary for better accuracy in children.

Keywords: Biomarker; Child; Diagnostic; Screening; Tuberculosis.