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?
MRI of the spine
Blood tests for anti-ganglioside antibodies
Nerve conduction studies
Lumbar puncture with cerebrospinal fluid analysis