RESUMEN
Objective: To detect the cell-free DNA of Mycobacterium tuberculosis (Cf-TB) in the cerebrospinal fluid (CSF) of patients with tuberculous meningitis (TBM), and to assess the diagnostic value of this method for TBM. Methods: We prospectively included patients with suspected meningitis from the Department of Tuberculosis, Beijing Chest Hospital, Department of Neurology, Beijing Chaoyang Hospital and Department of Neurology, 263 Hospital of the People's Liberation Army from September 2019 to March 2022. A total of 189 patients were included in this study. Among them, 116 were male and 73 were female, aged from 7 to 85 years, with an average of (38.5±19.1) years. The CSF specimens of the patients were collected for Cf-TB, MTB culture and Xpert MTB/RIF. SPSS 20.0 was used for statistical analysis and the difference was statistically significant with P<0.05. Results: Among the 189 patients, there were 127 patients in the TBM group and 62 patients in the non-TBM group. The sensitivity of Cf-TB was 50.4% (95%CI 41.4%-59.3%), the specificity was 100% (95%CI 92.7%-100.0%), the positive predictive value was 100% (95%CI 92.9%-100.0%), and the negative predictive value was 49.6% (95%CI 40.6%-58.6%). Using clinical diagnosis as the gold standard, the sensitivity of Cf-TB was 50.4% (64/127), which was significantly higher than that of MTB culture (8.7%, 11/127) and Xpert MTB/RIF (15.7%,20/127) (all P<0.001). Using etiology as the gold standard, the sensitivity of Cf-TB was 72.7% (24/33), which was significantly higher than that of MTB culture [33.3%, 11/33, (χ2=10.28, P=0.001)] and was similar to Xpert MTB/RIF (60.6%, 20/33) (χ2=1.091, P=0.296). Conclusion: The sensitivity of the Cf-TB test was significantly higher than that of CSF MTB culture and Xpert MTB/RIF. Cf-TB may provide evidence for earlier diagnosis and treatment of TBM.
Asunto(s)
Ácidos Nucleicos Libres de Células , Mycobacterium tuberculosis , Tuberculosis Meníngea , Humanos , Masculino , Femenino , Niño , Adolescente , Adulto Joven , Adulto , Persona de Mediana Edad , Anciano , Anciano de 80 o más Años , Mycobacterium tuberculosis/genética , Tuberculosis Meníngea/diagnóstico , Tuberculosis Meníngea/tratamiento farmacológico , Ácidos Nucleicos Libres de Células/uso terapéutico , Sensibilidad y Especificidad , Diagnóstico PrecozRESUMEN
A method for ray tracing in uniaxial crystals is presented. General formulas for the direction of extraordinary rays are obtained. The method used in this paper is simpler than the general method based on Huygens's construction, and its physical picture is clearer.
RESUMEN
A method of ray-tracing calculations for uniaxial optical components with curved surfaces is presented. A set of simple ray-tracing formulas is derived. With the spatial ray-tracing method in geometrical optics, by using a computer we plot spot diagrams of extraordinary-ray images formed by some crystal systems.