Essential of audiology: screening and post-screening

Abstract

Newborn hearing screening is a type of screening testfor the early detection of hearing loss. It can recognizewith good accuracy newborns affected by hearingimpairment allowing an early diagnosis and interventionand avoiding cognitive and linguistic deficits [1-6].The incidence of bilateral sensorineural hearing loss(SNHL) in Sicily is 2.35 cases per 1000 newborns; thisvalue increases to 2.95 if we consider also unilateral SNHL[2,3] and to 10 cases per 1000 births among infants at risk[7-9].A correct newborn hearing screening programme isbased on different protocols depending on the presence/absence of audiologic risk factors:† Newborns without risk factors: [1-3]Initial Hearing Screening (Step I):The initialscreening should be performed using Transient-Evoked Otoacoustic Emissions (TEOAEs) in the birthcenters as close to discharge as possible, preferably 12hours or more after birth. It is recommended that aninfant be referred for a re-screening (step 2) if s/hedoes not pass the initial screening or results cannot beobtained in one or both ears.Re-screening (Step II):The re-screening should beperformed in a second level center using TEOAEs andAutomated Auditory Brainstem Response (AABR). Ifan infant does not pass the re-screening or if resultscannot be obtained in one or both ears, s/he shall bereferred to the regional third level center for diagnosticaudiological evaluation.† Newborns with risk factors (JCIH 2007) [7-10]Initial Hearing Screening (Step I): The Initial Hear-ing Screening should be performed in a second levelcenter using TEOAEs and AABR. If an infant does notpass the initial screening or if results cannot beobtained in one or both ears, s/he shall be referred tothe regional third level center for diagnostic audiologi-cal evaluation.Screening variablesActually TEOAEs have a sensitivity of 100% and a specifi-city of about 70-95%. A higher TEOAEs specificity valuedepends on [1,2,11]:† Timing of TEOAEs recording† Trained and qualified personnel† PASS/REFER criteriaLimitations of screeningAudiologic screening does not identify:† Post-natal SNHL (prelingual or perilingual) ,mainly related to genetic causes [12,13]† ANSD (Auditory Neuropathy Spectrum Disorder):the main risk factors associated to ANSD are severejaundice, prematurity, respiratory distress, ototoxicdrugs (used to treat neonatal infections), genetic muta-tions (e.g. OTOF gene). The diagnosis of ANSD isusually based on the combination of absent or abnor-mal ABR with normal TEOAESs and/or cochlearmicrophonics (CM) [14].