RESPONSE To LETTER TO THE EDITOR ON PUBLICATION (2008)

To the Editor: Thank you for your interest in our research. First of all, we want to emphasize the totally different approach of our study. Don et al. (1) developed a diagnostic procedure Cochlear Hydrops Analysis Masking Procedure (CHAMP) using latency measures of wave V of brainstem auditory evoked potentials. Using CHAMP, they could correctly classify healthy controls from a very stringently selected subgroup of definite Ménière's disease (MD) patients with 100% sensitivity and 100% specificity. Our objective was to evaluate the applicability and diagnostic value of CHAMP in a clinical setting. We analyzed a consecutive series of patients with inner ear disorders and compared the CHAMP results between the different diagnostic categories of MD according to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) (2) and non-Ménière patients with otovestibular complaints. When analyzing only the subset of definite MD patients and selecting only the interpretable CHAMP tests, we also found a 100% sensitivity as in the study of Don et al., and none of our definite MD patients had a test within normal ranges (3). However, we found difficulties in interpreting test results in 49% of the cases because there was no clear wave V in the click +500 Hz response. It seems now that Don et al. confirmed our findings and experienced similar problems. In a recent article not mentioned in their letter, Don et al. examined another parameter, the "complex amplitude ratio," as a good alternative when the latency measure of the undermasked component is difficult to determine (4). In this new study, the same patient group and-except for 1 subject-the same control group were used. The fact that Don et al. had to do another type of analysis in their same study group jeopardizes with the initial 100% sensitivity and 100% specificity (1). The "complex amplitude ratio" method of analysis may be valuable, but it still has to be validated, and the scientific background has to be demonstrated and proven. The CHAMP test is based on the undermasking principle, which is basically comparable with traveling wave velocity (TWV) tests. The TWV principle is dependent on the process of inner ear pressure regulation and the compliance of the Reissner membrane, as explained in the discussion. Our research group performed a preliminary study comparing TWV test with electrocochleography tests in MD diagnosis. A correlation was found between the results of electrocochleography and TWV test. However, no significant correlation was found between the TWV test result and the symptoms like vertigo, hearing loss, tinnitus, and aural fullness evaluated separately (5). Also, Murray et al. (6) could not discriminate MD patients from non-MD patients with sensorineural hearing loss. We further highlight the experimental animal study challenging the fact whether lasting pressure changes occur in hydrops and hence increase pressure wave propagation (7). Objective tests for MD, such as electrocochleography, TWV test, or CHAMP, are not included in the diagnostic guidelines of the AAO-HNS because their value has not (yet) been established in the literature (2). A problem with developing objective tests for the diagnosis of MD is the lack of a gold standard. Recent studies with 3-T magnetic resonance imaging showed changes in the membranous labyrinth in MD patients (8,9). In the future, imaging can lead to in vivo diagnosis of certain MD and act as a gold standard in the diagnosis of MD evaluating noninvasive diagnostic tests such as CHAMP. This will eventually assess the real sensitivity and specificity. A number of technical issues addressed by the letter of Don et al. are specified hereafter. The mean hearing thresholds in the article were calculated using 0.5, 1, 2, and 3 kHz, as suggested in the tables. This corrects the "Methods" section, which was adapted in the galley proof. Table 5: Ear 37: the latency delay is 0.25 instead of 0.5. Hence, the classification of CHAMP test is correct. This illustrates the value of publishing raw data following the AAO-HNS (2). About Ear 2: this patient had all 4 hallmark symptoms of MD. In addition to this, she complained from recruitment. However, the hearing problem was subjective, and on repetitive audiograms, there was never a documented hearing loss. This leads to the classification of a possible MD. If possible, hearing was assessed on the same day as the CHAMP testing. Because of practical issues, this was not always possible. Ear 4 was left out because there was a time lap of more than 2 weeks between the audiogram and CHAMP testing. Concerning the calculation of sensitivity and specificity, we did calculate the sensitivity and specificity after excluding the noninterpretable tests. See page 702, paragraph "distribution of CHAMP tests in the different groups": "This provides a sensitivity of 31.25% and a specificity of 28%. If we exclude the noninterpretable CHAMP tests, analysis provides a sensitivity of 53% and a specificity of 70%…" Finally, we emphasize the importance of further refining noninvasive tests, which are essential for better treatment development and better follow-up of MD patients. Claudia F. J. De Valck Gerd M. E. Claes Floris L. Wuyts Paul H. Van de Heyning University Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University Research Centre for Equilibrium and Aerospace, Antwerp University Hospital, Edegem, Belgium [email protected]