Community-based referrals for electrodiagnostic studies in patients with possible carpal tunnel syndrome: what is the diagnosis?

Objectives: To determine what proportion of patients referred with a clinical suspicion of carpal tunnel syndrome (CTS) have negative electrodiagnostic studies and identify their clinical diagnoses and to identify clinical features that predict the outcome of electrodiagnostic testing in patients referred with suspected CTS.

Design: Retrospective review of patients consecutively referred to the electrodiagnostic center with suspected CTS over a 1-year period.

Setting: Community-based electrodiagnostic center.

Participants: Three hundred forty-eight patients with suspected CTS.

Interventions: Not applicable.

Main outcome measure: The diagnosis of CTS was based on the electrodiagnostic findings.

Results: Of the 348 patients enrolled, 179 (51.4%) had electrodiagnostic studies that were inconsistent with a diagnosis of CTS. Twenty-seven patients (15.1%) had other electrodiagnostic abnormalities (eg, ulnar neuropathy, cervical radiculopathy), whereas the remaining 152 (84.9%) patients had studies within normal limits. Seventy-one patients (46.7%) with normal studies were diagnosed with musculoskeletal disorders, with myofascial pain and musculotendinous strain being most common. By using a multiple logistic regression model, clinical variables that may predict the outcome of electrodiagnostic testing for CTS included gender, duration of symptoms, nocturnal symptoms, sensory symptoms, wrist pain, neck pain, pinprick sensation, abductor pollicis brevis strength, and thenar bulk.

Conclusions: Many patients referred to an electrodiagnostic laboratory with a clinical suspicion of CTS have other diagnoses, most commonly musculoskeletal disorders. Because these various conditions may be mistaken for CTS, the electrodiagnostic evaluation is therefore an important diagnostic tool. Although traditional clinical findings including Tinel and Phalen sign were found to have limited clinical use, further validation of the groups of positive and negative clinical features may potentially enable the referring physician to identify more accurately patients who would benefit most from electrodiagnostic testing.