Table VI.

Testing methods for diagnosis: objective and subjective diagnostic procedures are summarized by appropriate age, method, clinical application and main disadvantages.

Test	Age	Method	Clinical applications	Disadvantages
Objective tests
Otoacustic emissions	Since the second or third day of life	It is an acoustic phenomenon that can be measured in the ear canal; it is related to electromotive activity of the outer hair cells of the cochlea, and to re-amplification of the middle ear	First option test for newborn hearing screening (low cost, fast execution, reliability and validity) Useful to assess cochlear function when the auditory evoked response are absent (retrocochlear hearing loss)	No responses obtained in presence of middle ear disease and hearing loss exceeding 30-40 dB Information only about the normal function of the outer hair cells, but not the type or level of hearing loss Narrow frequency range studied (1-3 kHz) Technical limits (positioning the probe, cue obstruction, noise)
Auditory Brain-Stem Evoked Response (Abr)	Infants of 26 weeks gestational age (when myelination begins). This assessment should take place by the age of about 3 months. After 12-18 months, morphology and parameters are similar to those of adults	This type of auditory evoked potentials is a series of five to seven peaks arising from auditory nerve and brainstem structures occurring within 10 msec of the onset of a moderate -intensity click stimulus	Gold standard for screening of infants with audiological high risk (high reliability, low cost) Objective estimation of hearing thresholds Comfortable examination conditions (spontaneous sleep, sedation) Useful tool in non-cooperative children Allows differential diagnosis between cochlear and retrocochlear pathologies	Threshold evaluations (no more than 80-90 dB) restricted to frequencies between 1 and 4 kHz (spectral content of click) Too small amplitude of Wave I from the auditory nerve Disorders above the inferior colliculus not identifiable Caution in the definitive diagnosis of hearing loss in newborns because of the variability of neural maturational processes Difficult interpretation of responses in children with middle ear effusion
Auditory Steady-State Response	All ages	The ASSR are evoked by continuous tones (carriers) modulated in frequency and / or in amplitude. The response is given by a complex wave linked by a definite phase relationship to the stimulus	Conjugation between highintensity sound stimulation and frequential specificity Reconstruction of a reliable hearing threshold using tonal stimuli Increased correlation with medium-low frequencies	Results affected by sleepwake rhythm, movements of patient and administration of drugs
Electro Cochleography	All ages	Echocochleography studies the electrical responses generated by the cochlea following a massive sound stimulus Evoked potentials are recorded from electrodes placed in or near the cochlea.	Second option after ABR in the estimation of hearing threshold (high reliability) Better characterization of hearing loss compared to ABR Enhancing Wave I of the ABR Useful in cases of hearing loss with uncertain ABR response or no response	Invasive method that requires surgery and general anaesthesia Audiological evaluations restricted to the periphery and frequencies of 1-4 kHz High cost
Tympanometry	All ages	Test measures in terms of compliance the effects of changes in air pressure on the eardrum-ossicular system	Non-invasive method that requires no active participation by the patient (easy execution) Useful to detect middle ear disease especially in children	Under 6 months of life lower sensitivity of the method for increased distensibility of ear canal Additional tests are required (otoscopy, reflexes, tone audiometry) for an accurate definition of hearing loss
Acoustic Reflex	All ages	This test refers to the reflexive contraction of the intratympanic muscles resulting from high intensity sound stimulation	Useful in childhood hearing loss for the evaluation of middle ear function Assists in the diagnosis of neurological diseases	Despite numerous attempts, does not identify hearing threshold Additional tests are required
Subjective tests
CRIB-O-GRAM	0-6 months	It is based on observation of alarm, postural and psychoemotive reactions after sound stimulus	Useful preliminary test in infants	Non-specific evaluation of side Inter-individual variability Useful when combined with other tests Often mistaken interpretation of infant's reactions
Boel-test	6-12 months	This test evaluates unconditioned reflex of gaze direction after sound stimulation	Multifunctional test that combines visual to sound stimuli	Non-definitive method that requires additional diagnostic tests
Behavioural Observation Audiometry (BOA)	> 6 months	Relies on the observation of positive or negative behavioural responses of orientation and location of a sound in free field	BOA can provide useful insight into the quality of the child's auditory responsiveness The test can predict an audiometric curve which is useful in planning intervention	Operant discrimination procedure Behavioural responses to sound may not provide an exact auditory threshold
Visual Reinforcement Audiometry (VRA)	1-3 years	In VRA, conditioned head turns are reinforced by an attractive visual stimulus that is activated near the source of the sound that is presented	Test that measures binaural hearing thresholds in free field	Variability in responses due to several factors (age, conditioning of the child, emotional stress caused by environment, technical staff)
Conditioned Play Audiometry (train show, peep show)	2-5 years	Operant conditioning of behavioural responses to sound is an effective approach for older children, with change in response behaviour and in the reinforcement that is used. In this test children learn to engage in an activity each time they hear the test signal.	Provides a complete hearing test with binaural air and bone threshold and can guide diagnosis	Variability in responses due to several factors (age, conditioning of the child, emotional stress caused by environment, technical staff)