Diagnostic accuracy of laboratory methods for infectious meningitis and encephalitis

Meningitis and encephalitis are severe inflammations of the central nervous system with high morbidity and mortality. Diagnostic tests include cellular and biochemical parameter analyses of cerebrospinal fluid, bacterioscopy, culturing, Polymerase chain reaction (PCR) methods, and latex agglutination. We have reviewed the literature to assess the efficiency and accuracy of diagnostic methods for meningitis and encephalitis. Comparative studies that evaluated the clinical and laboratory diagnosis of meningitis and encephalitis were considered. The review was guided by two flowcharts and questions prepared by experts. Global and differential cytology showed high sensitivity for bacterial meningitis (up to 90%), but it was lower (30–70%) for viral meningitis. Gram bacterioscopy showed a sensitivity of 47–93% and a specificity of 86–100%; culturing for aerobic bacteria had a high sensitivity (82%) and specificity (100%) for bacterial meningitis; the blood culture had a sensitivity of 50–80% and a specificity of 95–100%; the culture for fungi was the gold standard for fungal meningitis, with a sensitivity of 30–80%, a specificity of 99%, a positive predictive value of 85%, and a negative predictive value of 98%; screening for cryptococcal antigens showed both sensitivity and specificity values at 98.9% (95% CI: 97.9–99.5%); rapid PCR for enteroviruses had a sensitivity of 90–100% and a specificity of 95–100%; the Biofire® FilmArray® Panel ME had a combined sensitivity of 89.5% (95% CI: 81.1–94.4%) and a specificity of 97.4% (95% CI: 94–98.9%); and metagenomics showed 61% sensitivity (95% CI: 33–83%) and 98% specificity (95% CI: 92–99%). Thus, adequate, sensitive, and specific tests are essential to correctly detect the causative agent of meningitis, reducing the unnecessary use of antimicrobials, hospitalization time, and associated morbidity and mortality.