Assessment of DP Threshold and its Test–Retest Reliability in Normal Hearing Individuals

Abstract

Purpose: Distortion Product (DP) threshold test has been recently introduced as a clinical tool that provides frequency specific quantitative information on hearing sensitivity in dB HL. However, due to the dearth of literature in determining its degree of reliability, the extent of confidence in the test results has not been estimated. Therefore, the present study aimed at establishing the normative of DP threshold values across test frequencies in normal hearing individuals and check for its test-retest reliability.Methods: Purposive sampling was utilized in the study wherein fifty normal hearing individuals in the age range of 18 to 30 years (x̅=24, σ=2.1) were considered. DP threshold test was carried out across test frequencies from 1 kHz to 8 kHz in measurement window of 50 dB HL and was re-examined after 15 days.Results: The range of DP threshold level was -5 to 20 dB HL in right ear and -5 to 25 dB HL in left ear across the test frequencies. It was found to have the mean difference ranging -0.02 to 1.06 dB HL across test frequencies between the two sessions. Non-parametric Wilcoxon Signed Ranks test was performed to assess test-retest reliability which revealed no statistically significant difference for both ears (<i>p</i>>0.05).Conclusions: Hence, the current study presents normative of DP threshold test along with variance, beyond which the fluctuations in outer hair cell functioning can be expected to have occurred. Moreover, it is found to have good test retest reliability between the two sessions suggesting good potentiality of the test in assessing outer hair cells functioning.