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Introduction: Recently Cochlear Hydrops Analysis Masking Procedure (CHAMP) has been introduced as a tool to diagnose cochlear hydrops. In this test responses to the clicks presented alone and to clicks with masking noise high-pass filtered at 8, 4, 2, 1 and 0.5 kHz, the cochlea is successively masked from 8 kHz and higher down to 0.5 kHz and higher, the peak latency of wave V increases. However, in individuals with the cochlear hydrops, the masking noise is insufficient such that the latency of wave V in the responses to the clicks and various high-pass masking noise conditions is similar to that of wave V in the response to clicks alone.
Need of the Study: Ideally, any new test should reliable in a normal population that has no known pathology. This allows examiners to identify conditions and variables that are consistent or not consistent in normal hearing individuals, to establish quantifiable ranges of normative values, and to develop appropriate testing conditions. There has been equivocal findings in terms of the sensitivity and specificity of the CHAMP in diagnosis of cochlear hydrops (Don, Kwong & Tanaka, 2005; De Valck, Claes, Wuyts & Van de Heyning, 2007; Ordonez-Ordonez,et al.,2009). If CHAMP analysis is to hold promise as a clinical tool for assessing the cochlear hydrops, it is necessary to determine whether the variations in responses across the different frequencies are constant or not. Second, it is critical to know that the evoked neural response patterns are not random and that neural response patterns are stable in normal hearing individuals over time.
Objective of the study: Main objective of the study was to find out the test-retest reliability of CHAMP analysis in normal hearing individuals.
Method: Fifteen subjects in the age range of 18 to 30 years, with a mean age of 19 years, participated in the study. They fulfilled the following criteria: 1. normal hearing thresholds in both the ears, as revealed by absolute pure tone thresholds of <15 dBHL from 250 Hz to 8000 Hz for air conduction and from 250Hz to 4000 Hz for bone conduction, 2. Normal middle ear functions as revealed by tympanometry and reflexometry evaluations. 3. Consent to participate in the study. CHAMP was done for all the subjects. In CHAMP, first clicks were presented alone and then clicks with masking different noise high-pass filtered at 8, 4, 2, 1 and 0.5 kHz. Only latency of wave V was measured in all the participants, as in the diagnosis of cochlear hydrops the latency of wave V is mainly considered. All the participants were retested with the same procedure once again after a gap of one week.
Results: Results showed that the mean latency of wave V increased, as the cochlea was successively masked from 8 kHz and higher down to 0.5 kHz. Mean and standard deviation for the latency of wave V was calculated for clicks presented alone and then clicks presented with masking different noise high-pass filtered at 8, 4, 2, 1 and 0.5 kHz. Results showed that the latency Variation was more for clicks presented with 0.5 kHz high pass masking noise, variation in latency, otherwise was less at other high pass masking noise and click presented alone. In the first trial, the mean latency for wave V for click alone was 5.54 msec for click and 8kHz high pass masking noise was 5.89 msec, for click and 4 kHz high pass masking noise was 6.29 msec, for click and 2 kHz high pass masking noise was 6.80 msec, for click and 1kHz high pass masking noise was 7.79 msec and for click and 500 Hz high pass masking noise was 8.35 msec. On retesting the the mean latency for wave V for click alone was 5.56 msec for click and 8kHz high pass masking noise was 5.92 msec, for click and 4 kHz high pass masking noise was 6.26 msec, for click and 2 kHz high pass masking noise was 6.63 msec, for click and 1kHz high pass masking noise was 7.62 msec and for click and 500 Hz high pass masking noise was 8.17 msec. A non-parametric test (Wilcoxson signed rank test) was done to find out the significance difference between the two evaluation for click alone and clicks presented with different high pass masking noise. Wilcoxson signed rank test failed to show any significant difference between the two evaluations (p>0.05), for clicks alone and clicks presented with masking different noise high-pass filtered at 8, 4, 2, 1 and 0.5 kHz.
Discussion: CHAMP evoked for clicks alone and clicks presented with masking different noise high-pass filtered at 8, 4, 2, 1 and 0.5 kHz show remarkable test-retest reliability when recorded from the same individual. Given this stability, it follows that any significant alterations in latency would likely reflect changes in neural response patterns, and not simply random variability.
Conclusion: The intent was to find out the test-retest reliability of the CHAMP analysis. The CHAMP analysis showed a remarkable test-retest reliability of the test. However, the same test-retest can be done in clinical population to find the sensitivity of the test. The test can also be used to monitor the progress in subjects with the cochlear hydrops. |
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