Validation of a Rapid Molecular Amplification Method for the Post-Mortem Diagnosis of Tuberculosis

A team of researchers from ISGlobal, the Manhiça Health Research Center (CISM) and Maputo Central Hospital (Mozambique) evaluates the feasibility of using a rapid and easy-to-use DNA amplification assay for the post-mortem diagnosis of tuberculosis (TB). The results, published in Nature Scientific Reports, validate the use of such technique for the detection of Mycobacterium tuberculosis, the bacterium that causes the disease, making it a valuable tool to improve the diagnosis of TB as cause of death.  

Tuberculosis is one of the leading causes of death in low and middle-income countries, where around one third of cases remain undiagnosed or unreported. Therefore, it is important to have specific and sensitive diagnostic tests that also work in autopsy studies.

The aim of the study was to determine whether the rapid molecular diagnostic test (called Xpert MTB/RIF) that is currently approved for detection of M. tuberculosis from sputum and cerebrospinal fluid, can also be used for diagnosis in tissues such as lung, brain and liver. To do so, they collected tissue samples from 30 adult patients who died at the Maputo Central Hospital and for whom a complete diagnostic autopsy was performed.  The Xpert assay dectected M. tuberculosis in lung tissue of 7 out of the 8 cases diagnosed with TB, with high sensitivity and specificity values (88 and 96% respectively) comparable to those of two other molecular amplification methods that were performed in parallel.   

The Xpert assay is faster and easier to use than other molecular methods, and therefore represents a valuable tool for the post-mortem diagnosis of TB. The study also shows a high hidden burden of TB among people who die of unknown causes, confirming that the use of post-mortem tests is crucial to better determine the TB mortality burden, particularly in countries like Mozambique where the case detection rate is low. 

This study is part of CaDMIA, a large project funded by the Bill and Melinda Gates Foundation, aimed at validating minimally invasive autopsies to determine causes of death in Mozambique and Brazil. 

Reference:

García-Basteiro, A. L. et al. The role of Xpert MTB/RIF in diagnosing pulmonary tuberculosis in post-mortem tissues. Sci. Rep. 6, 20703; doi: 10.1038/srep20703 (2016).