Outcomes with OAE and AABR screening in the first 48 hours : implications for newborn hearing screening in South Africa

Abstract

Despite the global focus on newborn hearing screening, this practice has remained almost exclusively reserved for the developed world (Olusanya, Luxon, & Wirz, 2004; Swanepoel, Hugo, & Louw, 2006). In South Africa, a developing country, estimates indicate that fewer than 10 per cent of newborns have any prospect of being screened for hearing loss (Theunissen & Swanepoel, 2008; Meyer, Swanepoel, Le Roux, & Van der Linde, 2012). Early discharge of newborns (<24 hours after birth) is an important barrier to successful newborn hearing screening (NHS) in South African hospitals, more specifically in the public health care sector, as healthy infants are discharged between 6 and 24 hours after birth (Government Communication and Information System, 2011; Mowbray Maternity Hospital, 2011). The objective of this study was to evaluate the outcomes of NHS within the first 48 hours, using an automated auditory brainstem response (AABR) device without the need for costly disposables, compared to transient evoked otoacoustic emissions (TEOAE) screening. This study used a quantitative approach employing a within-subject comparative quasi-experimental design to compare screening effectiveness of TEOAE and AABR techniques across different time intervals post birth (Shuttleworth, 2009; Hall, 1998; Leedy & Ormrod, 2001). NHS was performed on 150 healthy newborns (300 ears) with TEOAE and AABR techniques before discharge in a private hospital. A threestage screening protocol was implemented consisting of an initial screen with TEOAEs (GSI AUDIOscreener+) and AABR (Maico MB 11). Infants were screened at several points in time as early as possible after birth. Infants were only rescreened if either screening technique (TEOAE or AABR) initially yielded a refer outcome. The same audiologist (the researcher) performed all TEOAE and AABR screenings. Over the three-stage screen, findings indicated that AABR had a significantly lower referral rate of 16.7% (24/144 subjects) compared to TEOAE (37.9%; 55/145 subjects). Screening referral rate per ear showed a progressive decrease with increasing age. For both TEOAE and AABR, referral rate of ears for infants screened after 24 hours was significantly lower than for those screened before 24 hours. For infants screened before 12 hours after birth, the AABR referral rate per ear (51.1%) was significantly lower than the TEOAE referral rate (68.9%). Lowest initial referral rates per ear (TEOAE 25.8%, AABR 3.2%) were obtained after 48 hours post birth (Average age: TEOAE 61 hours post birth, AABR 57 hours post birth). In the light of the early hospital discharge typical in South Africa and other developing countries, screening with AABR technology is significantly more effective than screening with TEOAEs. AABR screening also has the advantage of identifying auditory neuropathy, and devices like the MB 11 that do not require disposables are particularly appropriate for developing countries with limited resources. Universal NHS protocols for contexts like South Africa may require AABR technology (without the burden of costs for disposables) in hospital-based settings for infants discharged after 24 hours. Otoacoustic emission (OAE) technology might be reserved for screening remaining infants once they are slightly older and attending routine health care visits such as immunisation clinics or midwife obstetric units.