Figure 4. Standard 2-tier and modified 2-tier algorithms for serodiagnosis of Lyme disease. The US Centers for Disease Control and Prevention recommended a standard 2-tier algorithm (A) and the modified 2-tier algorithm (B). *For patients with signs or symptoms consistent with Lyme disease for <30 days, the provider may treat and follow up with a convalescent-phase serum sample. Patients with erythema migrans should receive treatment on the basis of the clinical diagnosis. WB, Western blot.