Abstract:

Objective To investigate the diagnostic performance of Xpert MTB/RIF Ultra assay (Xpert Ultra) in the initial diagnosis of tuberculous meningitis among HIV-negative patients.Methods A total of 21 HIV-negative patients with suspected tuberculous meningitis from February to December 2018 were enrolled. Cerebrospinal fluid of all patients was examined for Mycobacterium tuberculosis with Xpert Ultra, Xpert MTB/RIF and liquid culture. According to the international diagnostic criteria for tuberculous meningitis, clinical score ≥6 points was used as the reference standard, and all patients were divided into tuberculous meningitis group (15 cases) and non-tuberculous meningitis group (6 cases). The sensitivity, specificity, positive predictive value, and negative predictive value of different diagnostic methods were compared.Results The cerebrospinal fluid of all 6 non-tuberculous meningitis patients was negative for Xpert Ultra, Xpert, and mycobacterial liquid cultures. Of the 15 patients with tuberculous meningitis, 10 (10/15, 66.7%) were positive for Xpert Ultra, 4 (4/15, 26.7%) were positive for Xpert, and 4 (4/15, 26.7%) were positive for liquid culture; Xpert Ultra was used for diagnosis of tuberculous meningitis with sensitivity of 66.7% (10/15), specificity of 100.0% (6/6), positive predictive value of 100.0% (10/10), and negative predictive value of 54.5% (6/11). Xpert was consistent with liquid culture for diagnosis of tuberculous meningitis, the sensitivity was 26.7% (4/15), specificity was 100.0% (6/6), positive predictive value was 100.0% (4/4), and negative predictive value was 35.3% (6/17). The difference of sensitivity among the three testing methods is statistically significant (χ ²=4.821,P=0.028). In the 10 Xpert Ultra positive patients, rifampicin resistance could not be determined in 3 patients (one test result was “very low” and another two were “trace call”), rifampicin resistance was not detected in the other 7 patients.Conclusion Xpert Ultra is the most sensitive method for diagnosing tuberculous meningitis and is recommended for initial diagnosis of tuberculous meningitis. When Xpert Ultra detects result is very low or trace call, there is a problem that rifampicin resistance cannot be determined, and further verification of drug resistance is needed.

Key words: Tuberculosis,meningeal, Cerebrospinal fluid, Diagnostic techniques and procedures, Bacteriological techniques, Molecular diagnostic techniques, Data interpretation,statistical