We are neurophysiologists at the Clinica Mangiagalli of Istituti Clinici di Perfezionamento in Milan. Our experience in neonatal audiologic screening, using TEOAE and ABR, started in 1995 as a part of a program of neurosensory evaluation of the newborn infant. Initially only infants coming from Neonatal Intermediate Care and from Neonatal Intensive Care Unit (NICU) were screened: newborns without audiological risk with TEOAE and ABR in case of fail; ABR were always performed in patients at risk. The criteria of audiological risk are those defined by the Joint Commettee on Infant Hearing (1994).

      Since 1997, following the recommendations of various international committees, we extended the screening to well-babies.

      The transient evoked otoacustic emissions (TEOAE) has been recorded with the ILO88 (Otodynamics) equipment, using the Quick-Screen acquisition mode, and with an automated device for otoemission Echoscreen (Madsen/Fischer-Zoth). The numerical criteria for PASS definition (conventional TEOAE) were: total reproducibility >= 70%, reproducibility in the 1.6 KHz frequency band >= 50%, in the 2.4-3.2-4 KHz bands >= 70%. The scoring of the response was done after a minimum of 50 sweeps averaged if pass criteria were met. In case of fail the test was prolonged beyond 260 sweeps on the basis of our personal expertise.

      The protocol consists of three steps for babies without audiological risk: in the first two steps the newborns are tested with TEOAE , in the third one they are tested with the conventional auditory brainstem responses (ABR).

Ist step: the screening protocol includes a first test (both ears ) at 36 hours of age for well babies; after that the infants who don't pass the initial test receive, if possible, a second examination with otoemissions prior to hospital discharge (the discharge is usually performed on third/fourth day for spontaneous delivery and on seventh day for cesarian section). This modality of conducting the screening has the aim of reducing the number of babies referred at the 2nd step as outpatients. This has to be taken in account when someone wants to evaluate the efficacy of the screening. The newborns coming from the neonatal intermediate care are examined before discharge usually to the age corresponding to the term .

2nd step: out-patient control with TEOAE 2-3 weeks after discharge; if they fail again they undergo at the 3rd step.

3rd step: the babies who fail the 2nd step are submitted to conventional ABR examination with threshold identification. If ABR responses show abnormalities (this is no response at 40 dBHL), the infants are retested one month later and then, in case of persistent hearing impairment, sent to the audiological unit to receive a comprehensive hearing evaluation (before six months of age).

       Newborns at audiological risk are submitted to the conventional ABR before the second month of corrected age, without taking in account the result of the TEOAE, considering the possibility of retrocochlear damage in this group.

       The tested population consists of 19290 babies without risk and 487 at risk. Among the no-risk babies 14390 were screened with conventional TEOAE and 4900 with automated TEOAE. The refers in the no-risk population at the first step were 470 (2.4%). At the second step the percentage of missed at follow-up was 12.8%, at the third step 15.6%. Conventional ABR were performed in 97 infants ( 0.5% of the whole population ) among them we found 19 (0.1%) pathological ABR. .Our screening program identified in the no-risk population 10 babies (0.5 per thousand) with bilateral hearing loss (>= 40 dBnHL in the best ear), among them 5 with severe-profound hearing loss; 8 (0.4 per thousand) with unilateral hearing impairment.

      In the risk group we found 23 babies (4.7%) with bilateral hearing loss (13 severe- profound ) and 22 (4.5%) with unilateral hearing loss.         It should be pointed out that of infants with bilateral hearing impairment 30.3% had no risk factors.

      The effectiveness of the screening must be periodically verified as feed-back of the work done and checked according to the guidelines of the American Academy of Pediatrics.

• The goal is the examination of 100% of the population in both ears; anyway a minimum of 95% of newborns must be screened successfully. In our situation such results can be only reached with a hospital based screening .
  
  
• The referral rate should no exceed 4%. This result can be reached only after a suitable training period and is strictly dependent from the improvement of the modalities of performing the test.
  
  
• In our experience the percentage of refers at the first step showed a strong decrease from 1997 (8%) to 2001 (1.2 %).
  
  
• Besides to obtain a lower referral rate, we decided to retest the newborns who did not pass, as many times as possible, before discharge, with a reduction of referred newborns of about 40%. This procedure also allows to reduce the number of the outpatients at the 2nd step of the follow-up and, in consequence, the number of subjects missed; this means also a reduction of the costs and less worries for the parents.
  
  
• The percentage of infants missed at follow-up can be reduced with a better organisation of the screening program and a better communication and collaboration with parents and pediatricians. In fact in the first six months of the year 2001 the percentage of infants missed has been 10% at the second step and 0% at the third step.
  
  
• The proportion of infants with significant hearing loss missed by the screening program have to be ideally equal to zero (false negative rate); it should be noticed that we found 4 newbors in the risk population who passed at TEOAE with a severe-profound hearing loss at ABR test, due to retrocochlear damage. It is our opinion that these findings give, one more time, a strong evidence that screening in risk population has to be done with ABR (conventional or automated).
  
  
• An universal neonatal hearing screening programs must have an acceptable cost-effective range which depends on a lot of factors; among which we think that the use of automated techniques for TEOAE, easier and time-saving, that can be administered by non particularly specialized nursery staff, can help in reducing costs.
  
  

Conctat: Dr. G. Pastorino and Dr. P.Sergi
Address: Istituti Clinici di Perfezionamento, U.O. Neurologia-Neurofisiopatologia, Via Commenda 12, 20122 Milano ( Italy).
Phone: +39 02 57992407
e-mail: icpnfc@tiscalinet.it