Assessment of the validity of masking in electrodiagnostic research.
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.
Haig
Andrew J
AJ
Spine Program, Department of Physical Medicine and Rehabilitation, University of Michigan Medical School, 325 East Eisenhower Parkway, Ann Arbor, MI 48108, USA.
Yamakawa
Karen
K
Kendall
Richard
R
Miner
Jennifer
J
Parres
Christopher M
CM
Harris
Marcus
M
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*