Related Experiment Video
Updated: Apr 1, 2026
Diagnosing Pulmonary Tuberculosis with the Xpert MTB/RIF Test
Published on: April 9, 2012
Improved diagnostic sensitivity for tuberculous meningitis with Xpert(®) MTB/RIF of centrifuged CSF
N C Bahr1, L Tugume2, R Rajasingham3
1Division of Infectious Diseases and International Medicine, Department of Medicine, University of Minnesota, Minneapolis, USA; Center for Infectious Diseases & Microbiology Translational Research, University of Minnesota, Minneapolis, Minnesota, USA; Infectious Disease Institute, Makerere University, Kampala, Uganda.
Background:
TB meningitis (TBM) diagnosis is difficult and novel diagnostic methods are needed. The World Health Organization recommends Xpert(®) MTB/RIF as the initial TBM diagnostic test based on two studies reporting suboptimal sensitivity (~50-60%).
Objective:
To study the effect of cerebrospinal fluid (CSF) centrifugation on Xpert performance for TBM detection.
Design:
A total of 107 predominantly human immunodeficiency virus (HIV) infected adults with presumed meningitis were screened prospectively in Kampala, Uganda. CSF was tested using 1) microscopy for acid-fast bacilli; 2) MGIT™ culture; 3) Xpert of 2 ml of unprocessed CSF; and 4) Xpert of centrifuged CSF. Diagnostic performance was measured against an a priori composite reference standard of any positive CSF tuberculosis test.
Results:
Of 107 participants, 18 (17%) had definite TBM. When CSF was centrifuged, Xpert had better sensitivity (13/18, 72%) than when using 2 ml of unprocessed CSF (5/18, 28%; P = 0.008). The median centrifuged CSF volume was 6 ml (IQR 4-10). Mycobacterial culture yielded 71% (12/17) sensitivity at a median delay of 27 days. Only 39% were positive by both culture and centrifuged Xpert, with additional cases detected by Xpert and culture.
Conclusions:
CSF centrifugation optimizes the diagnostic performance of Xpert in the detection of TBM. A combination of culture and Xpert detected the largest number of cases.
