Confirmation Bias and Specificity of Electromyography for Radiculopathy (P3.164)

OBJECTIVE: To assess: 1. how history and physical exam influence EMG interpretation (confirmation bias); 2. the true specificity and sensitivity of EMG using blinded reviewers; 3. inter- and intra-rater agreement of EMG. BACKGROUND: Despite routine use of EMG in practice, no study has evaluated its predisposition to confirmation bias (history/exam influencing the results of the test) or its specificity. There is only scant literature assessing inter- and intra-rater reliability. We evaluate these parameters. DESIGN/METHODS: A standard root screen was performed using needle EMG in normal subjects and patients with radiculopathy. Radiculopathy was defined by a clinical gold standard. Three CDs of the same 20 EMG recordings in varying order were created. Three electromyographers from different academic centers evaluated each CD independently one month apart. The first two CDs were evaluated without clinical information. CD-3 included history and examination findings. Evaluators provided their interpretation using an ordinal scale for denervation and reinnervation and a diagnosis: normal or radiculopathy, and if radiculopathy, the level(s), duration and severity. Descriptive statistics were used. RESULTS: Specificity of EMG for diagnosis of radiculopathy was 77[percnt]; sensitivity was 73[percnt]. Sensitivity was 40[percnt] for mild-moderate radiculopathy and increased to 80[percnt] for moderate-severe radiculopathy. Availability of clinical information changed diagnosis in only 2/60 recordings; both changes concurred with the clinical information. Mean intra-rater reproducibility was 80[percnt] (all subjects), 87[percnt] (radiculopathy) and 73[percnt] (normals). Mean inter-rater agreement was 63[percnt] (all subjects), 70[percnt] (radiculopathy) and 53[percnt] (normals). Inter-rater agreement for denervation was 91[percnt], but only 60[percnt] for reinnervation. CONCLUSIONS: Although confirmation bias is present in the EMG assessment of radiculopathy, it is likely not large. EMG specificity for detecting radiculopathy is fair (77[percnt]). Intra-rater reproducibility is good (80[percnt]). Inter-rater agreement is high for denervation (91[percnt]) but only modest (60[percnt]) for reinnervation. Sensitivity improves with increasing severity of radiculopathy. Support: K24 NS060951 Disclosure: Dr. Narayanaswami has received personal compensation for activities with Blue Cross Blue Shield of Massachusetts, Advanced Medical, and Boston Clinical Research Institute. Dr. Geisbush has nothing to disclose. Dr. Jones has nothing to disclose. Dr. Weiss has received personal compensation for activities with Walgreens, Grifols, and Nufactor. Dr. Weiss has received research support from Clinical Trials Research Unit/Northeast ALS Consortium and the ALS Therapy Alliance. Dr. Mozaffar has received personal compensation for activities with California Stem Cell Inc., NuFactor, Crescent-Walgreens, Crescent Healthcare, Biogen Idec, CSL Behring, Genzyme, Baxter, and Grifols. Dr. Mozaffar has received research from Cytokinetics, Dr. Rutkove has received personal compensation for activities with Convergence Medical Devices as a consultant. Dr. Rutkove has received royalty payments from UpToDate and Springer.