Distal Symmetric Neuropathy: Too Many Useless Tests

A recent review shows that guidelines and testing for patients with distal symmetric polyneuropathy (DSP) can and should be improved. Brian C.Callaghan, MD, MS of the Department of Neurology at the University of Michigan in Ann Arbor, and colleagues reviewed recently published articles on distal symmetric polyneuropathy. Their conclusions appear in the Journal of American Medicine.

There are few studies on DSP, but those that do exist show that diabetes is the most frequent cause. Approximately 10-34% of people with type 1 diabetes develop the condition, and 8-25% of those will type 2 diabetes have it. Peripheral neuropathy “encompasses all disorders that result in injury to nerves within the peripheral nervous system” and DSP is one of the most common types. Patients with DSP “present with numbness, tingling, pain, or a combination of these that typically starts in their toes and slowly spreads proximally.”

In 2009, the American Academy of Neurology (ANN) suggested the most useful tests for people with peripheral neuropathy are “fasting glucose, vitamin B12, serum protein electrophoresis with immunofixation, and glucose tolerance tests.” However, many physicians routinely order “a large number of tests, with great variation in the type of tests ordered,” and even then, “the ANN-recommended tests are not often performed.”

Magnetic resonance imaging (MRI) of the brain and spine, as well as electrodiagnostic tests are both expensive, and of limited value for patients with peripheral neuropathy. Although these tests are ordered for 80% of the people with the condition, they lead to a change in disease management in only 2 out of 458 cases.

Patients with DSP are too often not treated for pain. Three classes of pharmaceuticals have been shown to help manage neuropathic pain. The researchers suggest that physicians “start with a medication from 1 of these 3 classes based on patient comorbidities, potential adverse effects, and cost.” Glucose control is effective to prevent DSP associated with type 1 diabetes, but it is unknown if it is an appropriate therapy for those with type 2 diabetes-associated DSP.

The researchers conclude “Advances have been made regarding which diagnostic tests should be used for patients with DSP; however much work remains to be done.” Too often, too many expensive tests are ordered and patients are not being treated for pain. Further research is necessary to identify new, effective therapies.