Relationship of Head Circumference and Age in the Prediction of the Real-Ear-to-Coupler Difference (RECD).

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.

Alternative metrics for real-ear-to-coupler difference average values in children.

BACKGROUND: Ideally, individual real-ear-to-coupler difference (RECD) measurements are obtained for pediatric hearing instrument-fitting purposes. When RECD measurements cannot be obtained, age-related average RECDs based on typically developing North American children are used. Evidence suggests that these values may not be appropriate for populations of children with retarded growth patterns. PURPOSE: The purpose of this study was to determine if another metric, such as head circumference, height, or weight, can be used for prediction of RECDs in children. RESEARCH DESIGN: Design was a correlational study. For all participants, RECD values in both ears, head circumference, height, and weight were measured. STUDY SAMPLE: The sample consisted of 68 North American children (ages 3-11 yr). DATA COLLECTION AND ANALYSIS: Height, weight, head circumference, and RECDs were measured and were analyzed for both ears at 500, 750, 1000, 1500, 2000, 3000, 4000, and 6000 Hz. A backward elimination multiple-regression analysis was used to determine if age, height, weight, and/or head circumference are significant predictors of RECDs. RESULTS: For the left ear, head circumference was retained as the only statistically significant variable in the final model. For the right ear, head circumference was retained as the only statistically significant independent variable at all frequencies except at 2000 and 4000 Hz. At these latter frequencies, weight was retained as the only statistically significant independent variable after all other variables were eliminated. CONCLUSIONS: Head circumference can be considered as a metric for RECD prediction in children when individual measurements cannot be obtained. In developing countries where equipment is often unavailable and stunted growth can reduce the value of using age as a metric, head circumference can be considered as an alternative metric in the prediction of RECDs.