New test strongly improves TB diagnosis

A Brazilian research group together with AIGHD researchers studied the effect of rolling out a cartridge-based molecular tuberculosis assay (Xpert MTB/RIF) for routine diagnosis of TB in two cities in Brazil, Rio de Janeiro and Manaus.

The study, funded by the Bill and Melinda Gates Foundation, was designed as a stepped wedge or phased implementation trial among 14 public laboratories that provide TB diagnosis in these cities. Lab records were linked to TB notification records.

The study showed 1,137 TB diagnoses among 11,705 patients using the standard microscopic sputum smear examination, and 1777 diagnoses among 12,522 patients using the novel assay. Expressed as rates of TB diagnosis in the population, Xpert MTB/RIF increased the rate of bacteriologically confirmed diagnosis by 59%, but did not significantly change the total rate of TB diagnosis. This discrepancy was due to the fact that the rate of diagnosis without any lab testing (i.e. based on clinical criteria only, for which the proportion of patients that truly have TB is unknown) did not change during the 8 months study period.

The conclusion is that rolling out Xpert MTB/RIF as an alternative to sputum smear examination strongly improves laboratory diagnosis of TB, and that clinicians should make more use of lab tests now that more sensitive TB assays are available. The study results prompted the Brazilian government to implement the Xpert MTB/RIF test in the national laboratory network.

Read the article: Impact of Replacing Smear Microscopy with Xpert MTB/RIF for Diagnosing Tuberculosis in Brazil: A Stepped-Wedge Cluster-Randomized Trial