Laboratory testing in peripheral nerve disease.

Selecting appropriate laboratory tests in diagnosing peripheral neuropathies is important because it increases the yield of correct diagnoses and is cost effective. A large number of tests are available. This article provides a guide to selecting appropriate tests and reviews the clinical situations that suggest specific tests. Electrodiagnostic testing is valuable in almost all patients with peripheral neuropathy. Quantitative sensory testing adds additional information and is especially useful in patients with small fiber neuropathy. On occasion, routine blood tests may discover metabolic disorders causing a patient's neurologic disorder. A number of antibody assays for neuropathies are available commercially, with the most useful being anti-MAG, anti-GM1, anti-GQ1b, anti-Hu, and anticalcium channel antibodies, but only in very select situations and not as "screening studies". The role of cutaneous nerve and skin biopsies in selected disorders is discussed.