title: Predicting the degree of hearing loss using click auditory brainstem response in babies referred from newborn hearing screening.
abstract: OBJECTIVE
  The predictive ability of the auditory brainstem response (ABR) is an important factor governing the program sensitivity of neonatal hearing screens. The study examined the accuracy of the click-evoked auditory brainstem response (ck-ABR) when undertaken below the age of 6 months (from expected date of delivery) in predicting the pure-tone thresholds subsequently found to be present in children with a congenital permanent childhood hearing impairment.
  
  
  METHODS
  Children with permanent childhood hearing impairment were ascertained from neonatal screening programs that have been subject to longitudinal evaluation. Ninety-two children who had ck-ABR recorded when below 6 months of age and repeatable ear specific pure-tone audiometry were recruited. Those with recognized temporary middle ear effusions at either test were excluded. The relationship between ABR and pure-tone thresholds was tested using the Pearson correlation coefficient with a linear regression model used to estimate pure-tone threshold (dependent variable) from ABR (independent variable). Correlation coefficients were obtained for pure-tone frequencies at octave intervals between 0.25 kHz and 4 kHz and at various frequency combinations. The difference between ABR and pure-tone threshold was analyzed. Those with a difference of greater than 20 dB were further examined. The ABR and pure-tone differences were also compared in babies born at term and prematurely.
  
  
  RESULTS
  Of the 92 children recruited to the study two children had a confirmed auditory neuropathy spectrum disorder (2%) and 10 (11%) had an audiometrically confirmed progressive hearing impairment. When these children were excluded, there was a high linear positive correlation (r = 0.90, SE = 14.3 dB) between the ABR and pure-tone thresholds averaged at 2 to 4 kHz. Although the correlation varied for different audiometric configurations, in all cases with a sloping hearing loss the correlation with their best frequency was weaker than the correlation at 2 to 4 kHz. For the total cohort the mean difference between ABR and pure-tone thresholds averaged at 2 to 4 kHz was 4.4 dB (SD = 19.29). The modal difference was 0 dB (58%) and 76 % had a difference of 20 dB or less. ABR underestimated the subsequently recorded pure-tone thresholds by more than 20 dB in 11 children and 10 of these children showed progression of their hearing loss measured by serial pure-tone audiometry. ABR overestimated the pure-tone thresholds by more than 20 dB in 15 children. Nine of these children (60%) had suffered a perinatal illness and the mean difference between the pure-tone and ABR thresholds was significantly greater in those born at <35 weeks of gestation (p < 0.001).
  
  
  CONCLUSIONS
  There is a high positive linear correlation between ck-ABR and pure-tone average thresholds at 2 to 4 kHz. However, the predictive value of ABR is reduced in certain neonatal groups. The cause for this is discussed as are the implications for undertaking a test battery at this age to improve the predictive accuracy.
authors: Department of Audiology, Whipps Cross University Hospital, London, UK. margaret.baldwin@bartshealth.nhs.uk
authors: Margaret
authors: M
authors: Baldwin
authors: Peter
authors: P
authors: Watkin
mesh_terms: D001301:Audiometry, Pure-Tone / Q000379:methods*; D001309:Auditory Threshold / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D004739:England; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D034381:Hearing Loss / Q000175:diagnosis*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D015997:Neonatal Screening / Q000379:methods*; D011237:Predictive Value of Tests