Inter- and intraobserver variation in the interpretation of electromyographic tests.

This study was undertaken with the aim of evaluating inter- and intraobserver variation on the pathophysiological interpretation of individual electromyographic (EMG) tests on muscles and nerve segments. Seven physicians from 6 European EMG laboratories independently interpreted 81 EMG studies comprising 735 muscle tests and 726 tests on nerve segments. Pathophysiological conclusions were inferred from findings of these tests without considering clinical information. For most combinations of findings, both the inter- and intraobserver variations on the interpretation were low, suggesting that common criteria for pathophysiological interpretations were used and that these were used consistently. For some combinations of findings, however, there was disagreement on whether these indicated specific or unspecific pathophysiological changes. In particular disagreement on whether findings indicated demyelination may be of clinical significance. A large part of the intraobserver variation may be explained by a change towards more cautious interpretations during the study for most of the physicians. It is concluded that there is a need to seek for consensus on the pathophysiological interpretation of individual findings and for incentives to ensure consistency in interpretations. The fact that experienced physicians changed their ways to interpret findings during the study suggests that agreement may be improved globally.