Approach to polyneuropathy Quiz: Ace Your Exams

A 31-year-old man presents to the primary care clinic for evaluation of weakness. Two days ago, the patient’s legs felt heavy, which was attributed to exercise. This morning, the weakness worsened, and the patient started tripping on the stairs. A review of systems reveals recent gastrointestinal symptoms, including diarrhea and abdominal cramping. The patient feels unable to catch his breath. There is no significant past medical history, and no daily medication is taken. Temperature is 37.0°C (98.6°F), pulse is 82/min, respirations are 18/min, blood pressure is 120/72 mmHg, and oxygen saturation is 96% on room air. There is symmetric bilateral weakness with ankle dorsiflexion and knee flexion and extension, as well as a loss of vibration sense. Deep tendon reflexes are absent in the bilateral lower extremities. Which of the following laboratory study results is most likely to be associated with this patient’s diagnosis?