MS-2001

A 49-year-old man presents to the hospital with complaints of weakness in his legs and tingling sensation in his feet. His wife noticed a problem with his gait over the past few weeks. The patient also reports increasing forgetfulness. During examination, the Romberg test is positive. The patient has a medical history of Crohn’s disease and is currently on treatment with 5-aminosalicylic acid and prednisone. A peripheral blood smear shows the presence of larger than normal and pale red blood cells. What laboratory finding is most likely to be present in this patient?