Performance of the Xpert MTB/RIF Ultra assay for determining cause of death by tuberculosis in tissue samples obtained by minimally invasive autopsies

Abstract

An estimated 1.5 million deaths were attributable to TB in 2018.1 However, some uncertainty exists as to the exact global figures, given that approximately 30% of incident cases are not diagnosed, and because of the difficulties of ascertaining TB as cause of death (CoD).2 Undoubtedly, complete diagnostic autopsies (CDAs) constitute the gold standard for establishing a diagnosis of TB at death. However, CDAs are seldom performed in high-TB-burden countries because of the scarcity of trained pathologists, the time-consuming nature of the procedure, and the meager acceptability of the practice by relatives.3 In recent years, an alternative minimally invasive autopsy (MIA), a procedure well accepted by the next of kin, has been developed.4 ,5 MIA can be conducted relatively rapidly with the use of biopsy needles for sampling key organs, which leave barely visible marks, which is thus more acceptable to relatives. This method has shown good sensitivity for diagnosing TB as CoD.6 Nonetheless, MIA has thus far used standard histological and microbiological approaches for TB diagnosis (identification of granulomatous lesions, acid-fast bacilli smears, in-house polymerase chain reaction methods),7 which remain time consuming, require specific expertise, and have limited sensitivity. Thus, we evaluated the diagnostic accuracy of the molecular Xpert MTB/RIF Ultra (hereafter referred to as Xpert Ultra) assay in samples obtained by MIA to detect CoD by TB.