Describe an additional laboratory test that could be used to confirm the diagnosis of one of the patients who is not infected with meningitis.

Meninges refers to the three layes of membranes surrounding the brain and spinal cord of the mammals. The inflammation of these protective membranes of the brain and the spinal cord caused by the infection of bacteria, virus or other microorganisms is called the meningitis.

A laboratory test to identify or rule out meningitis is the analysis if the cerebrospinal fluid (CSF) by lumbar puncture. CSF is a colorless fluid filling the ventricles of the brain and the central canal of the spinal cord. Lumbar puncture is a techinque of isolating the CSF from the sac sround the spinal cord using a needle under a local anesthetic. The sample is then analysed for the opening pressure which is normally between 6 and 18 cm of water in a patient who is not infected with meningitis. Also, the levels of glucose in CSF is above 40% of that in blood in non-infected persons. If lactate levels are less than 35mg/dl, this will also rule out meningitis.