• A J Haig, H M Tzeng, and D B LeBreck.
• Department of Physical Medicine and Rehabilitation, The University of Michigan, Ann Arbor 48109-0042, USA.
• Arch Phys Med Rehabil. 1999 Oct 1; 80 (10): 1273-81.

ObjectivesTo determine whether electrodiagnostic testing changes diagnostic certainty compared with a detailed history and physical examination, and whether interactions between medical information, the extent of testing, and diagnostic certainty imply a need for advanced medical knowledge on the part of the tester.DesignProspective observation.SettingUniversity orthopedic department and small community hospital electrodiagnostic laboratories.PatientsTwo hundred fifty-five consecutive referrals for upper extremity nerve complaints.Outcome MeasuresDiagnosis, diagnostic confidence, and severity of neurologic lesion were coded after standardized history and physical and after electrodiagnostic testing.ResultsElectrodiagnostic testing substantially altered 42% of diagnoses, confirmed 37%, and did not clarify 21%. The extent of testing correlated with the size of the differential diagnosis, the number of previous hospitalizations, and the number of other medical problems. Confidence in final diagnoses correlated positively with severity of the lesion, but negatively with the size of the differential diagnosis and the number of painful body areas. Hospitalizations and medical problems also tended towards negative correlations.ConclusionsThis study, in which all electrodiagnostics, histories, and physical examinations were performed by a single physician, suggests that electrodiagnosis substantially alters clinical impressions in a large percentage of patients. The complex relationship between clinical information, the extent of testing, and final diagnostic certainty suggests that specialized medical knowledge is required for accurate electrodiagnosis.

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