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Monofilament testing insufficient to diagnose peripheral neuropathy

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Monofilament testing alone is inadequate for diagnosing peripheral neuropathy, according to a systematic literature review done by physicians in The Netherlands.

As the authors note in the Annals of Family Medicine for November/December, “Monofilament testing is an inexpensive, easy-to-use, and portable test for assessing the loss of protective sensation, and it is recommended by several practice guidelines to detect peripheral neuropathy in otherwise normal feet.”

But in fact, Dr. Jacquelien Dros at the University of Amsterdam and colleagues report, “little can be said” about the test’s accuracy for detecting neuropathy in feet without ulcers.

The research team reviewed diagnostic studies in which testing with 5.07/10-g monofilaments was compared to nerve conduction for accuracy in detecting peripheral neuropathy of any cause in patients without visible foot ulcers.

Their literature search turned up only 3 studies that met inclusion criteria, with 37, 126, and 478 subjects, respectively. Each study, however, focused only on patients with diabetes.

The sensitivity of the monofilament test ranged from 41% to 93%, and the specificity ranged from 68% to 100%.

The authors suggest that “these wide ranges are possibly due to differences in application of the monofilament (number and site), interpretation of the monofilament test (definition of thresholds), and differences in study populations.” This clinical heterogeneity prevented performance of a meta-analysis.

Dr. Dros and associates recommend further research on monofilament testing, focusing on optimal standards for test application and on defining a reproducible test threshold.

They concur with the recommendation of the American Diabetes Association that diagnosis of peripheral neuropathy requires a clinical examination with more than one test.

“Tests for this clinical examination are vibration perception (using a 128-Hz tuning fork), pressure sensation (using a 10-g monofilament at least at the distal halluces), ankle reflexes, and pinprick,” the investigators advise. “When in doubt, a nerve conduction test might be necessary to establish a firm diagnosis.”

Ann Fam Med 2009;7:555-558.