Which diagnostic test is associated with elevated protein levels in the cerebrospinal fluid for diagnosing Guillain-Barre Syndrome?

In diagnosing Guillain-Barré Syndrome, a lumbar puncture is the diagnostic test associated with elevated protein levels in the cerebrospinal fluid (CSF). This procedure allows for the collection of CSF, which can then be analyzed for various components, including protein concentration. In Guillain-Barré Syndrome, the CSF often shows elevated protein levels while typically exhibiting a normal white blood cell count, a characteristic finding known as albuminocytologic dissociation. This feature helps differentiate Guillain-Barré from other neurological disorders that may present with similar symptoms.

The other diagnostic tests listed do not have the same relevance for identifying Guillain-Barré Syndrome. A CT scan may be useful for ruling out other conditions but does not provide information specific to CSF composition. An MRI of the brain can help evaluate other neurological conditions but does not generally aid in the diagnosis of Guillain-Barré. A chest X-ray is primarily used to assess lung and heart conditions and has no direct correlation with the diagnosis of Guillain-Barré Syndrome. Therefore, the lumbar puncture is pivotal in confirming the diagnosis due to its revealing of elevated protein levels in the CSF.