Objective
To evaluate the added value of the electrodiagnostic examination (EDX) on the clinical diagnosis.

Methods
Electrodiagnostic and clinical findings from 482 patients collected randomly from five Danish centers were entered in a web database and peer-reviewed electronically and at face-to-face meetings by neurophysiologists. The diagnosis reached by consensus was considered gold standard and compared with the referral diagnosis in diagnostic sub-groups: motor neurone disorders (46 patients), polyneuropathies (132), myopathies (15), root lesions (25), plexus lesions (44), neuromuscular transmission disorders (12), and upper and lower limb entrapments (150 and.58 patients).

Results
EDX confirmed the referral diagnosis in 188 (39%), excluded it in 218 (45%), and changed it in 49 (10%) of the patients. In the remaining 27 (6%) the referral diagnosis was possibly confirmed. In the different diagnostic sub-groups the referral diagnosis was most often confirmed in upper limb entrapments (51%) and polyneuropathies (49%), most often excluded in myopathies (80%) and root lesions (72%), and most often changed in plexus lesions (25%) and lower limb entrapments (22%).

Conclusions
EDX changes or excludes the clinical working diagnosis in more than half of the patients, which may have significant impact on management.

Key message
EDX adds valuable information to the clinical diagnosis.