title: Assessment of the validity of masking in electrodiagnostic research.
abstract: OBJECTIVE
  Performed by thousands of specialists and researched for >60 yrs, electrodiagnostic testing rates poorly in evidence-based guidelines in part because there are no valid masked research studies. This study assesses whether the electrodiagnostic examination can be adequately masked.
  
  
  METHODS
  Prospective, controlled, masked trial. A total of 150 persons aged 55-80 yrs, thought clinically to be asymptomatic (n = 32), with low back pain (n = 46), or with spinal stenosis (n = 63), underwent needle electromyography and nerve conduction studies by specialists in physical medicine and rehabilitation who were not permitted to ask any clinical information or to perform a formal examination. Examiners rated potential bias and recorded clues that might bias the examination.
  
  
  RESULTS
  Examiners noted potential for bias in conversation in 17 and due to pain behavior in one. Half of these potential unmaskings pointed away from the correct clinical diagnosis, leaving potential for bias in <6% of the subjects. The clinical diagnosis had no relationship to electrodiagnostician rating of pain behavior in response to testing or repositioning, to limb atrophy, and to arthritis (P > 0.05 all instances).
  
  
  CONCLUSIONS
  The electrodiagnostic examination can be successfully masked. This information will help future research in electrodiagnostics meet the criteria of evidence-based medicine.
authors.affiliation: Spine Program, Department of Physical Medicine and Rehabilitation, University of Michigan Medical School, 325 East Eisenhower Parkway, Ann Arbor, MI 48108, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Haig
authors.forename: Karen
authors.initials: K
authors.lastname: Yamakawa
authors.forename: Richard
authors.initials: R
authors.lastname: Kendall
authors.forename: Jennifer
authors.initials: J
authors.lastname: Miner
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Parres
authors.forename: Marcus
authors.initials: M
authors.lastname: Harris
mesh_terms: D000368:Aged; D004576:Electromyography; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D010808:Physical Examination; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D016037:Single-Blind Method; D013130:Spinal Stenosis / Q000150:complications* / Q000175:diagnosis*