title: Critically re-evaluating a common technique: Accuracy, reliability, and confirmation bias of EMG.
abstract: OBJECTIVE
  (1) To assess the diagnostic accuracy of EMG in radiculopathy. (2) To evaluate the intrarater reliability and interrater reliability of EMG in radiculopathy. (3) To assess the presence of confirmation bias in EMG.
  
  
  METHODS
  Three experienced academic electromyographers interpreted 3 compact discs with 20 EMG videos (10 normal, 10 radiculopathy) in a blinded, standardized fashion without information regarding the nature of the study. The EMGs were interpreted 3 times (discs A, B, C) 1 month apart. Clinical information was provided only with disc C. Intrarater reliability was calculated by comparing interpretations in discs A and B, interrater reliability by comparing interpretation between reviewers. Confirmation bias was estimated by the difference in correct interpretations when clinical information was provided.
  
  
  RESULTS
  Sensitivity was similar to previous reports (77%, confidence interval [CI] 63%-90%); specificity was 71%, CI 56%-85%. Intrarater reliability was good (κ 0.61, 95% CI 0.41-0.81); interrater reliability was lower (κ 0.53, CI 0.35-0.71). There was no substantial confirmation bias when clinical information was provided (absolute difference in correct responses 2.2%, CI -13.3% to 17.7%); the study lacked precision to exclude moderate confirmation bias.
  
  
  CONCLUSIONS
  This study supports that (1) serial EMG studies should be performed by the same electromyographer since intrarater reliability is better than interrater reliability; (2) knowledge of clinical information does not bias EMG interpretation substantially; (3) EMG has moderate diagnostic accuracy for radiculopathy with modest specificity and electromyographers should exercise caution interpreting mild abnormalities.
  
  
  METHODS
  This study provides Class III evidence that EMG has moderate diagnostic accuracy and specificity for radiculopathy.
authors.affiliation: From the Department of Neurology (P.N., T.G., S.B.R.), Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA; the Department of Neurology (L.J.), Mayo Clinic, Rochester, MN; the Department of Neurology (M.W.), University of Washington, Seattle; the Department of Neurology (T.M.), University of California, Irvine; and the Department of Neurology (G.G.), University of Kansas Medical Center, Kansas City. pnarayan@bidmc.harvard.edu.
authors.forename: Pushpa
authors.initials: P
authors.lastname: Narayanaswami
authors.affiliation: From the Department of Neurology (P.N., T.G., S.B.R.), Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA; the Department of Neurology (L.J.), Mayo Clinic, Rochester, MN; the Department of Neurology (M.W.), University of Washington, Seattle; the Department of Neurology (T.M.), University of California, Irvine; and the Department of Neurology (G.G.), University of Kansas Medical Center, Kansas City.
authors.forename: Thomas
authors.initials: T
authors.lastname: Geisbush
authors.affiliation: From the Department of Neurology (P.N., T.G., S.B.R.), Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA; the Department of Neurology (L.J.), Mayo Clinic, Rochester, MN; the Department of Neurology (M.W.), University of Washington, Seattle; the Department of Neurology (T.M.), University of California, Irvine; and the Department of Neurology (G.G.), University of Kansas Medical Center, Kansas City.
authors.forename: Lyell
authors.initials: L
authors.lastname: Jones
authors.affiliation: From the Department of Neurology (P.N., T.G., S.B.R.), Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA; the Department of Neurology (L.J.), Mayo Clinic, Rochester, MN; the Department of Neurology (M.W.), University of Washington, Seattle; the Department of Neurology (T.M.), University of California, Irvine; and the Department of Neurology (G.G.), University of Kansas Medical Center, Kansas City.
authors.forename: Michael
authors.initials: M
authors.lastname: Weiss
authors.affiliation: From the Department of Neurology (P.N., T.G., S.B.R.), Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA; the Department of Neurology (L.J.), Mayo Clinic, Rochester, MN; the Department of Neurology (M.W.), University of Washington, Seattle; the Department of Neurology (T.M.), University of California, Irvine; and the Department of Neurology (G.G.), University of Kansas Medical Center, Kansas City.
authors.forename: Tahseen
authors.initials: T
authors.lastname: Mozaffar
authors.affiliation: From the Department of Neurology (P.N., T.G., S.B.R.), Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA; the Department of Neurology (L.J.), Mayo Clinic, Rochester, MN; the Department of Neurology (M.W.), University of Washington, Seattle; the Department of Neurology (T.M.), University of California, Irvine; and the Department of Neurology (G.G.), University of Kansas Medical Center, Kansas City.
authors.forename: Gary
authors.initials: G
authors.lastname: Gronseth
authors.affiliation: From the Department of Neurology (P.N., T.G., S.B.R.), Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA; the Department of Neurology (L.J.), Mayo Clinic, Rochester, MN; the Department of Neurology (M.W.), University of Washington, Seattle; the Department of Neurology (T.M.), University of California, Irvine; and the Department of Neurology (G.G.), University of Kansas Medical Center, Kansas City.
authors.forename: Seward B
authors.initials: SB
authors.lastname: Rutkove
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000068598:Data Accuracy; D004576:Electromyography / Q000379:methods / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation*; D011843:Radiculopathy / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D014741:Video Recording; D055815:Young Adult