A 45-year-old patient presents to the emergency department with progressive weakness in both legs, spreading to the arms over the past week. The patient also reports tingling sensations in the fingers and toes. Which of the following is the BEST initial diagnostic test to confirm the suspected diagnosis of Guillain-Barré syndrome?
Nerve conduction studies
MRI of the spine
Lumbar puncture with cerebrospinal fluid analysis
Blood tests for anti-ganglioside antibodies