1.2), accompanied by a control antibody
index of less than 1.0 and a Albumin
ratio of less than 0.0078, is strong evidence for intrathecal synthesis of organism-specific antibody, and thus CNS involvement by B. burgdorferi. Elevation of either the control antibody index, the albumin ratio, or both may indicate leakage of antibody across the blood brain barrier which may falsely elevate the B. burgdorferi Antibody Index.