[Clinical and Laboratory Diagnosis of Central Nervous System Infections]

Central nervous system (CNS) infections, including acute encephalitis, bacterial meningitis, tuberculous meningitis, and fungal meningitis, represent a potentially life-threatening neurological emergency. An etiological diagnosis of CNS infection is made a definite diagnosis based on the identification of pathogenic agents in the CNS using cerebrospinal fluid (CSF) smears or cultures, the identification of pathogenic antigens in CSF, the identification of pathogenic products in brain tissues or CSF with polymerase chain reaction (PCR), or the identification of specific antibody responses in CSF. Since time is required to obtain results from these laboratory tests, initial empirical treatments for the suspected CNS infection are required. The optimal specimen sampling and delivery is an essential requirement to reach the definite diagnosis. Nucleic acid amplification tests, such as PCR assays, show high sensitivity and specificity in detecting pathogens from CSF. In Japan, most genetic tests for pathogenic agents are performed as part of academic research. The number of commercially available genetic tests is limited. Moreover, no genetic tests for pathogenic agents in the CSF are covered by the national health insurance system in Japan. To manage the continuity of genetic tests, this inefficient system should be improved.