To evaluate for the potential for other conditions, it would be appropriate to consider several blood tests in the initial evaluation of the patient with suspected MS. These tests include complete blood count (CBC), antinuclear antibodies (ANA), serum test for syphilis (RPR, VDRL, etc.), fluorescent treponemal antibody test (FTA), Lyme titer, ESR and, possibly, angiotensin converting enzyme level (a test for sarcoidosis). Imaging (MRI if at all possible) should be performed to rule out alternative diagnoses and because MRI can provide information about dissemination of disease. Over 90% of patients with MS have abnormalities on the MRI scan. Multifocal white matter disease of MS is easily observed but not easily differentiated from vascular lesions, gliotic scars or other forms of inflammation (see Chap. 11 ). As yet, there are no entirely pathognomonic criteria for MS on an MRI scan, but McDonald criteria are used in research studies. Spinal fluid examination may show evidence of immunologic activity in the CNS: slight elevation of mononuclear white blood cells (pleocytosis) is often found, and CSF oligoclonal IgG bands and increased globulin to albumin ratio can be found in 90% of cases. There may also be an increase in CSF myelin basic protein levels, which is evidence of actual damage to myelin. Evidence of subclinical demyelinated lesions can be provided by MRI, visual, somatosensory, or brain stem auditory evoked responses. The "hot bath test" is an historically interesting test. A hot bath often amplifies symptoms and worsens deficits by raising body temperature (which slows conduction in demyelinated plaques).