Accelerating extrapulmonary tuberculosis diagnosis with a rapid molecular assay

Area of Science:

• Microbiology
• Infectious Diseases
• Molecular Diagnostics

Background:

• Extrapulmonary tuberculosis (EPTB) presents diagnostic challenges due to low bacterial load and atypical symptoms.
• Conventional diagnostic methods for EPTB often have long turnaround times, delaying treatment initiation.

Purpose of the Study:

• To evaluate the benefits of systematically using nucleic acid amplification tests (NAAT) for diagnosing EPTB in a developed country.
• To assess the time savings and diagnostic performance of reflex NAAT on extrapulmonary specimens.

Main Methods:

• A prospective study from November 2017 to March 2021 included 691 extrapulmonary samples.
• Samples were tested using both conventional methods and Xpert MTB/RIF Ultra (NAAT).
• Time to results and diagnostic performance metrics were evaluated.

Main Results:

• Nucleic acid amplification test (NAAT) identified 85 (12.3%) positive samples for Mycobacterium tuberculosis complex.
• NAAT results were available in an average of 1.3 days, compared to 18 days for culture, accelerating diagnosis by 16 days.
• Overall NAAT sensitivity was 87.9% and specificity was 94.6%, with low invalid result rates (0.9%).

Conclusions:

• Systematic use of NAAT offers a rapid and consistent diagnostic approach for EPTB.
• This molecular test can significantly accelerate EPTB diagnosis and treatment initiation, days to weeks earlier than culture.
• NAAT provides a valuable tool for timely management of extrapulmonary tuberculosis.