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Electrodiagnostic and Ultrasonographic Evaluation is of Little Value in Patients with High Clinical Suspicion of Carpal Tunnel Syndrome
Christopher M. Gibbs, MD1; John R. Fowler, MD2
1University of Pittsburgh Medical Center, Pittsburgh, PA; 2Department of Orthopaedics, University of Pittsburgh Medical Center, Pittsburgh, PA

Introduction: Prior studies demonstrate that the probability of carpal tunnel syndrome (CTS) based on clinical evaluation does not significantly change following electrodiagnostic testing (EDS). Ultrasound (US) has been introduced as a viable method for diagnosing CTS, but its effect on the diagnostic probability of CTS has not been well studied and would be useful for value-based care. The purpose of this study was to evaluate the change in probability of CTS following EDS and US testing. It was hypothesized that EDS and US testing would be of low value for most patients.
Methods: Two-hundred ninety-five patients being assessed for compressive neuropathies of the upper extremity were prospectively enrolled to be evaluated using the Carpal Tunnel Syndrome 6 (CTS-6) questionnaire, EDS, and US. The CTS-6 questionnaire was used to calculate the pretest probability of CTS based on clinical history and examination. Bayesian analysis was used to calculate the posttest probability of CTS following EDS and US using reports of sensitivity and specificity derived from the literature. Pearsons correlation and the average and absolute changes between pre- and posttest probabilities were calculated (p <0.05).
Results: The pretest probability of CTS was 0.74 0.29 (range: 0.11-0.99). A pretest probability of ?0.8 and ?0.5 was seen in 61% and 16% of patients, respectively. The probability of CTS following EDS testing increased for all patients (Table 1), with the greatest mean change seen with pretest probability <0.5 (0.31 0.36). With US, the largest change in probability occurred in patients with a pretest probability <0.5 (0.23 0.16). For patients with CTS-6 score >17, an absolute change ?0.10 was seen in 0% of patients following EDS and 15% of patients following US (p <0.01).
Discussion: The main finding of this study is that for patients with a high clinical suspicion of CTS (CTS-6 >17), adjunctive testing is of little value. The posttest probability of CTS increased in all patients following EDS testing and in patients with low pretest probability following US suggesting that for patients with a low pretest probability, adjunctive testing is likely to increase the probability of CTS and result in potentially unwarranted treatment. This information is useful for guiding diagnostic decision making in the evaluation of CTS to avoid inappropriate resource utilization or intervention.


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