Improved diagnostic sensitivity for tuberculous meningitis with Xpert(®) MTB/RIF of centrifuged CSF.

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.

The effect of sodium hypochlorite and ethylenediaminetetraacetic acid irrigation, individually and in alternation, on tooth surface strain.

AIM: To evaluate the effect of irrigation regimens on tooth surface strain using saline, sodium hypochlorite (3% and 5% NaOCl) and ethylenediaminetetraacetic acid (17% EDTA), individually and in alternating combinations. METHODOLOGY: Single-rooted premolar teeth with single canals prepared to standardized dimensions were grouped by anatomical features and randomly distributed amongst six experimental groups (n = 12 each). The six groups were: (1) saline; (2) 5% NaOCl; (3) 3% NaOCl; (4) 17% EDTA; (5) 3% NaOCl and 17% EDTA; (6) 5% NaOCl and 17% EDTA. All groups underwent four (group 1) or five (groups 2, 3, 4, 5, 6) sequential 30-min irrigation periods following each of which the tooth was subjected to a standard regime of cyclic, nondestructive, occlusal loading. Tooth surface strain was measured during each loading cycle using electrical strain gauges mounted cervico-proximally. The data were analysed by Hierarchical anova and post hoc multiple comparisons. RESULTS: Irrigation with 5% NaOCl alone or alternating with 17% EDTA significantly (P < 0.001) increased the peak strain values for each of the irrigation periods compared with that of saline (group 1). The data for the other groups revealed no significant differences compared with those of saline. The strain increase after the fourth irrigation cycle was significantly higher for group 6 than for group 2. The measured canal morphology and dentine thickness parameters did not prove to have a significant effect on tooth surface strain. CONCLUSIONS: Irrigation with 5% NaOCl acting alone or alternated with 17% EDTA (used in 30 min cycles), significantly increased tooth surface strain. The alternated regimen showed significantly greater changes in tooth surface strain than NaOCl alone. Irrigation with 3% NaOCl and 17% EDTA individually or in combination did not significantly alter the tooth surface strain.