RISK 6 transcriptomic signature for diagnosis and treatment monitoring of extrapulmonary tuberculosis

Abstract

Diagnosing extrapulmonary tuberculosis (EPTB) is challenging due to the diverse clinical manifestations of the disease and the requirement for invasive sampling and specialized processing. Moreover, current methods lack the ability to monitor or predict treatment efficacy even though standard EPTB treatment regimens often require extension. In this context, we aimed to evaluate the performance of the RISK6 transcriptomic signature, previously investigated solely in pulmonary TB, for EPTB diagnosis and treatment monitoring. 29 individuals (> 11 years old) presumed to have EPTB and 10 healthy controls, were enrolled from the clinical facility from March 2022 to 2023. Clinical samples from presumed cases underwent GeneXpert, culture, and, microscopy testing for the diagnosis of EPTB. Blood samples were obtained from all participants at enrolment (and post-treatment for confirmed cases) to assess the RISK6 signature score via RT-qPCR. RISK6 signature performance was evaluated using the receiver-operating characteristic curve (ROC AUC) and Student’s t-test. Among 29 presumptive individuals tested, 15 were microbiologically confirmed for EPTB and 14 were unconfirmed (tested negative). Ongoing RISK6 score analysis is available for 15 confirmed cases at baseline (13 with post-treatment scores), 14 unconfirmed cases, and 10 controls. RISK6 effectively discriminated confirmed cases from controls (AUC of 92%, sensitivity 93%, specificity 80%) and unconfirmed cases (AUC of 84%, sensitivity 93%, specificity 73%). Furthermore, RISK6 scores for confirmed cases decreased significantly (p < 0.001) post-treatment. The findings in this study suggest that the RISK6 signature performance for EPTB meets the biomarker test criteria defined by the target product profile released by WHO. Minimally invasive, this signature can potentially transform EPTB diagnosis by providing an accessible testing option, even for challenging cases lacking sufficient evidence for biopsy. Additionally, the signature’s post-treatment performance indicates a future role in helping clinicians elucidate treatment outcomes.