Improved diagnosis of childhood tuberculous meningitis using more than one nucleic acid amplification test

Abstract

Background: Early treatment is critical to reducing tuberculous meningitis (TBM) related morbidity and mortality. Diagnosis based on cerebrospinal fluid (CSF) culture is impractical due to slow turnaround times, while microscopy has poor sensitivity. Enhanced detection methods are essential to guide early treatment initiation, especially in vulnerable young children.

Methods: We assessed the diagnostic accuracy of the GenoType(®) MTBDRplus and Xpert(®) MTB/RIF assays on CSF collected from paediatric meningitis suspects prospectively enrolled at Tygerberg Hospital, Cape Town, South Africa. Fluorescent auramine-O microscopy, liquid culture for Mycobacterium tuberculosis, GenoType and Xpert assays were performed on all CSF samples.

Results: Of 101 meningitis suspects, 55 were diagnosed with TBM and 46 served as non-TBM controls. Using a pre-defined TBM case definition as reference standard, sensitivities and specificities were 4% and 100% for fluorescent microscopy, 22% and 100% for culture, 33% and 98% for GenoType, 26% and 100% for Xpert, 22% and 100% for microscopy and culture combined and 49% and 98% for GenoType and Xpert combined. Culture, GenoType and Xpert combined performed best, with 56% sensitivity and 98% specificity.

Conclusion: Although commercial nucleic-acid amplification tests performed on CSF revealed incrementally improved diagnostic accuracy, providing rapid microbiological confirmation, they cannot serve as a rule-out test.