American Society for Peripheral Nerve

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A Comparison of Ultrasound and Electrodiagnostic Testing for the Diagnosis of Carpal Tunnel Syndrome Using a Validated Clinical Tool as the Reference Standard
John Fowler, MD1; Maria Munsch, BS2; Joseph E. Imbriglia, MD2; William Hagberg, MD2
1Orthopaedic Surgery and Sports Medicine, University of Pittsburgh, Pittsburgh, PA; 2Hand and Upper Ex Center, Wexford, PA

Introduction: Current guidelines recommend obtaining a confirmatory test in patients with a clinical diagnosis of carpal tunnel surgery for whom surgical treatment is being considered. Electrodiagnostic testing (EDX) is currently considered the gold standard, but is uncomfortable for patients, time consuming, and potentially costly. A previously developed, validated clinical diagnostic tool that combines findings from the history and physical exam has been shown to make EDX unnecessary in a select group of patients with high pre-test probability. Ultrasound (US) has similar sensitivity and specificity to EDX and the advantages of being painless and faster. The purpose of this study is to compare the sensitivity and specificity of US and EDX using a validated diagnostic tool as the reference standard.

Methods: After obtaining Institutional Review Board approval, all patients in an upper extremity practice, referred for EDX for any reason, were recruited to participate in this study. A blinded, certified electrodiagnostic technician performed all EDX testing. A distal motor latency > 4.2 ms or distal sensory latency > 2.2 ms was considered positive. A blinded, hand fellowship trained surgeon measured the cross-sectional area (CSA) of the median nerve at the level of the pisiform using a portable ultrasound machine. A CSA > 10 mm2 was considered positive. The Carpal Tunnel Syndrome 6 (CTS-6) diagnostic tool was completed for each patient based on his/her history and physical examination. A score greater than or equal to 12 on the CTS-6 was considered a positive diagnosis for carpal tunnel syndrome and less than 12 was considered a negative diagnosis. The sensitivity and specificity of EDX and US were calculated using CTS-6 as the reference standard.

Results: 100 patients, 64 females and 36 males, participated in the study. 70 patients had a positive diagnosis by CTS-6 criteria. The sensitivity and specificity of US was 85% and 93% respectively. The sensitivity and specificity of EDX was 77% and 95% respectively.

Conclusion: While US will not replace EDX in complicated cases, in a select group of patients with a positive CTS-6, US can be used to confirm the diagnosis of carpal tunnel syndrome with a better sensitivity and comparable specificity to EDX.

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