To diagnose meningitis, a physician will review a child’s medical history and perform a physical examination. Certain medical tests may also be performed, including:

• Spinal tap. The insertion of a long needle into the spinal canal to collect cerebrospinal fluid (CSF) for laboratory testing. Analysis of CSF is the only definitive diagnosis method of meningitis. CSF is checked for indicators of an infection (e.g., the number of white blood cells, glucose and protein levels) and then analyzed by a physician to determine if meningitis is present. CSF may also help identify if the source of infection is bacterial or viral. A spinal tap is nearly always performed if meningitis infection is suspected.
  
  
• Throat culture. The back of the throat is swabbed and examined under a microscope. A throat culture can determine if the presence of microorganisms that can cause meningitis or a disease with similar symptoms (e.g., encephalitis) are present. In addition, it may also be helpful in determining the appropriate course of treatment.
  
  
• Imaging tests. Tests that produce images of internal body organs, tissues, structures and pathways (e.g., x-ray, CAT scan, MRI). Imaging tests of certain parts of the body (e.g., chest, skull) may show swelling or inflammation consistent with meningitis and the severity of the infection.
  
  
• Urine tests. Urine may be tested to check for the source of infection.
  
  
• Blood tests. Blood may be analyzed to check counts of white and red blood cells and biochemistry (hormone levels). Cultures of blood can be developed that can be examined for the presence of bacteria or viruses.
  
  
• Polymerase chain reaction (PCR). A process that checks blood for the presence of viruses or parasites. A PCR may be performed if a child is suspected of having meningitis.
  
  
• Biopsy.  Rarely, a sample of tissue from a rash thought to be caused by meningitis may be removed for laboratory analysis.