Validity of clinical small-fiber sensory testing to detect small-fiber degeneration

(Ridehalgh, Sandy-Hindmarch, & Schmid, 2018)

Aims: To examine the validity of clinical tests to assess small nerve fibers degeneration using Carpal Tunnel Syndrome (CST) as a model neuropathy.

Methods: Prospective cross-sectional. Presence of CTS was assessed with skin biopsies. 85 patients with CTS were evaluated with Neurotip and Quantitative sensory testing (T°). A subgroup of 51 CTS was tested with toothpick and coins.

Results: None of the test in isolation has sufficient validity in isolation. However, reduced pinprick has LR+3,94 and Sp=0,88 and can help rule in small fiber degeneration (not toothpick). Negative cold and warm with coin has LR-0,14, Se=0,98 and can help rule out small fibers degeneration. More severe easier to rule in, less severe more difficult to rule out.

Issues: Tested only on upper arm and may be different in ≠ areas of body less innervated. Excluded other small nerve neuropathies, or other issues that may be present in clinical practice. + and – LR are weak, the study shows which is the best indicator but among relatively weak tools. Use of control may inflate Sp and LR+.

Practice: Use pinprick test first, if positive then we can rule in pathology. If negative, cold warm coin detection is needed to rule out small-fiber degeneration. Just clinical suspicion: Gold standard in needed to confirm diagnosis.

Ridehalgh, C., Sandy-Hindmarch, O. P., & Schmid, A. B. (2018). Validity of Clinical Small–Fiber Sensory Testing to Detect Small–Nerve Fiber Degeneration. Journal of Orthopaedic & Sports Physical Therapy, 48(10), 767–774.

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