Defining the Level of Abnormal ECOG in a Neurotology Practice

Abstract

Objective: 1) Identify the different levels of sensitivity and specificity of electrocochleography (ECOG) in our laboratory setting as normal or abnormal SP/AP ratio; and 2) select the level of specificity as the desired parameter of the abnormal SP/AP ratio of ECOG.

Method: This retrospective study reviews 61 patients undergoing ECOG in our vestibular laboratory who were diagnosed with unilateral endolymphatic hydrops (Ménière syndrome or cochlear hydrops) on the basis of clinical findings, audiogram, and vestibular studies. Sensitivity and specificity levels of ECOG in our laboratory are reported across various SP/AP ratios.

Results: Sensitivity and specificity levels of ECOG obtained in our vestibular laboratory are demonstrated for SP/AP ratios ranging from greater than 30% to greater than 50%. These data are the following: 1) greater than 30% (sensitivity, 0.72; specificity, 0.57); 2) greater than 35% (sensitivity, 0.66; specificity, 0.84); 3) greater than 40% (sensitivity, 0.52; specificity, 0.92); 4) greater than 45% (sensitivity, 0.43; specificity, 0.98); and 5) greater than 50% (sensitivity, 0.28; specificity, 0.98).

Conclusion: Inherent inter-site testing variability requires that each laboratory should set its own level of “abnormal” for ECOG. This study demonstrates sensitivity and specificity for ECOG at different ratios. For our use as a confirmatory test, we selected 80% specificity and set 35% as our abnormal SP/AP ratio.