Biochemical tests of cerebrospinal fluid help aid in diagnosis, such as the presence of encephalitis caused by microbial infections such as tuberculosis and bacteria; lumbar puncture, which is required for cerebrospinal fluid tests, also helps to determine the level of intracranial pressure. Biochemical tests of the cerebrospinal fluid include tests for sugar, protein, and chloride in the cerebrospinal fluid. The level of these indicators helps to help identify the cause of encephalitis and meningitis. If the protein level is elevated, it suggests the possible presence of multiple sclerosis, optic neuromyelitis optica, and Guillain-Barre syndrome. If sugar and chloride levels are decreased, tuberculosis or a bacterial infection may be present. Cerebrospinal fluid testing requires a lumbar puncture to extract the cerebrospinal fluid. The intracranial pressure can be tested before the specimen is retained, which helps to understand the severity of the disease and aids in diagnosis. Please operate and interpret the results under the guidance of a medical professional.