Relationship of Head Circumference and Age in the Prediction of the Real-Ear-to-Coupler Difference (RECD)
Journal of the American Academy of Audiology
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Background Pediatric hearing instrument fitting is optimally performed with individually obtained real-ear-to-coupler difference (RECD) measurements. If these measurements cannot be obtained, predicted values based on age are used. Recent evidence obtained from children aged 3-11 years suggests that head circumference (HC) may be a viable alternative or addition to age for use in RECD prediction. Purpose The purpose of the present study was to determine if HC can be used to predict RECDs in infants, children, and adults. Research Design A correlational design was used. HC and RECD values were measured in all participants. Study Sample Participants were 278 North American infants and children (136 males and 142 females) aged 1.6 months to 11 years and 109 adults (42 males and 67 females) aged 18 years to 83 years. Data Collection and Analysis After otoscopic inspection and immittance measurements were performed to assess candidacy for inclusion in the study, HC was measured twice for all participants and a single RECD measure was obtained for each participant at twelve frequencies (250 through 12500 Hz). The reliability of HC measurements was assessed with an intraclass correlation analysis. Linear regression analyses were performed with age and HC as predictor variables and RECDs as the dependent variable. Results Analysis indicated good reliability of the HC measurement. The relationships between RECD and HC were comparable with the relationships between RECD and age. Combining HC and age did not improve predictive accuracy. Conclusions HC can be used in children and adults as an alternative metric in the prediction of RECDs when individual RECDs cannot be obtained.