For vasa nervorum compromise or asymmetric axonal polyneuropathies, tests for hypercoagulable states and parainfectious or autoimmune vasculitis, particularly if suggested by clinical findings, should be done; the minimum is Erythrocyte sedimentation rate Serum protein electrophoresis Measurement of rheumatoid factor, antinuclear antibodies, and serum creatine kinase (CK) CK may be elevated when rapid onset of disease results in muscle injury.