A 50-year-old man has had a nonhealing ulcer on the bottom of his foot for 2 months. On examination, the 2-cm ulcer overlies the right first metatarsal head. There is a reduced sensation to pinprick in his feet. His visual acuity is reduced bilaterally. Laboratory studies show serum creatinine is 2.9 mg/dL. Which of the following laboratory test findings is he most likely to have?