significant hearing loss is one of the most frequent congenital diseases present at birth occurring in about 1 to 3 of every 1,000 healthy neonates and 2 to 4 of every 100 neonates in the neonatal intensive care unit ( nicu ) population [ 1 , 2 ] , although the prevalence of hearing loss varies because of differences in criteria for defining hearing impairment , the age group surveyed , and the testing methods used . environmental causes of hearing loss includes , for example , rubella embryopathy , prematurity , bacterial meningitis , and head trauma . the initial signs of hearing loss are very subtle , and systematic neonatal hearing screening is the most effective means of early detection . the early identification of congenital hearing loss is necessary to minimize the consequences of hearing impairment on the future communication skills of a baby [ 4 , 5 ] . the joint committee on infant hearing ( jcih ) has set 3 goals : screening should be completed by 1 month of age , diagnosis should be made by 3 months , and intervention and treatment should commence by 6 months . this was achieved by technologic advances in automated neonatal hearing - screening technology , resulting in the introduction of universal neonatal hearing screening ( unhs ) . transient evoked otoacoustic emissions ( teoaes ) are the most adequate hearing screening tests because they are accurate , economic , and of simple execution . in recent years , automated auditory brain stem response ( aabr ) instruments have been developed for screening neonates in hospital setting in order to identify patients with auditory neuropathy , and it is also important to reduce the number of false - positives .   in egypt , there is a relatively high prevalence of consanguineous marriage together with poor antenatal care and lack of public awareness about the importance of hearing screening . therefore , despite the presence of reliable screening methods ( teoaes , abr ) and effective methods of management , unhs programs are still not available . on the other hand , targeted neonatal hearing screening ( tnhs ) or risk - based hearing screening of neonates with risk factors for hearing loss is considered a compromise between no screening at all and unhs . accordingly , this study was conducted to compare the targeted , risk - based hearing screening and screening of the well - baby populations . a secondary aim was to investigate the frequency and the relative importance of each risk factor for hearing loss among the at - risk neonates . this prospective cohort study was conducted at the nicu and well - baby nursery populations , ain shams university hospital , between march 2009 and march 2010 on 150 neonates . one hundred consecutively admitted neonates with high - risk registry for hearing loss as listed by jcih   comprised the targeted screening group or the at - risk group while 50 full - term consecutive births of non consanguineous parents , in the well - baby nursery , with no risk factors for hearing loss comprised the control group . exclusion criteria were neonates whose admission lasted for less than 48 hours , and neonates died before the age of 3 months or did not attend an indicated abr at 3 months . in fact , 42 out of 51 ( 82.3% ) children with failed initial screening have attended the subsequent abr assessment . all neonates were subjected to the following : detailed medical , perinatal , and family history and thorough clinical examination with an emphasis on estimation of gestational age and assessment of apgar score at 1 and 5 minutes . otological examination included external examination of auricles and otoscopic examination for patency and structure of external auditory canal , tympanic membrane structure , and consistency . laboratory investigations included complete blood count ( cbc ) with differential leucocytic count using coulter counter gen - s ( beckman coulter , usa ) . diagnosis of hyperbilirubinemia was done by measuring total serum bilirubin level using hitachi 911 analyzer ( boehringer , germany ) and interpretation of the results according to the age - specific nomogram   which recommends responses ranging from careful monitoring to phototherapy or , ultimately , exchange transfusion . neonates were classified into 3 groups ; group a ( high - risk group ) included 50 neonates with multiple ( 3 - 4 ) risk factors for hearing loss ; group b ( low - risk group ) included 50 neonates with only one risk factor , and group c ( control group ) included 50 healthy neonates . it was done by the same observer ( h. m. taha , md ) using a two - staged teoaes screening tests , where initial teoaes were done immediately after birth followed by a retest prior to hospital discharge , and then failures of this second stage were referred for the diagnostic abr assessment after 3 months . the study protocol was approved by the local ethical committee of ain shams university . the teoaes were elicited using click stimuli with intensity ranging between 79 and 90  db spl with a mean of 83  3  db slp using a portable teoaes screener , vivosonic integrity 500 . better stimulus levels were associated with better probe fit and quiet state of the infant . the software determined the amplitude of the teoaes in five frequency bands : 1 , 1.5 , 3 , 4 , and 5  khz . testing was done while infants were naturally sleeping or were alert and calm ( no sedatives were used ) . if during the test infants were active or crying , the test could not be completed , and retesting was performed on another day . the results of teoaes were interpreted according to the rhode island criteria ; pass : response is 3  db or more in at least 4 frequency bands , partial pass : positive response in at least 2 frequency bands , and fail : no response is present in any frequency band . retesting was done for infants before hospital discharge , and those with failed or partial pass response in one or both ears for the second time were considered as failed screening and referred for diagnostic abr . recordings were done in the audiology unit , ain shams university hospitals , using the evoked response audiometry ampliad , model mk 12 . infants were naturally sleeping . three surface electrodes were placed so that the active electrode was applied to the forehead and the reference and ground electrodes to the ipsilateral and contralateral mastoids , respectively . duration were presented at a rate of 21  p / sec . at 90  db  nhl and down to threshold . a total of 1024 sweeps were differentially amplified through a band pass filter of 3003000  hz with 10  msec . analysis time . assessment of an abr pass was based on the detection of  wave v  at its expected latency ( 5.4 milliseconds ) according to our norms and down to threshold ( 30  db  nhl ) . neonates with type ( b ) tympanometry received medical management until the resolution of middle ear effusion and abr was retested when immittancemetry revealed type ( a ) or ( c ) tympanogram . abnormal results of abr were interpreted as permanent congenital hearing loss ( pchl ) with failed test of a 40  db  nhl in the presence of normal middle ear function . a recall of the diagnosed neonates for reevaluation was done using air and bone conduction abr . for bone conduction , abr bone vibrator was placed on the mastoid with effective masking applied to the other ear while testing . the data were recorded , coded , entered , and processed on computer using spss computer software ( version 15 ) . comparison between categorical variables was performed using chi - square (  ) test or fischer 's exact test when frequencies were below five . significant risk factors of hearing loss were entered into a multivariate analysis to determine the magnitude of the association between these factors and hearing loss and identify its odds ratio . a p value < 0.05 was considered significant in all analyses . most of the studied neonates were delivered by caesarian section ( cs ) ; 35/50 ( 70% ) in low - risk and 34/50 ( 68% ) in high - risk groups . moreover , 31/50 ( 62% ) of neonates in control group were delivered by cs and stayed for longer duration in the well - baby nursery than those who were delivered vaginally which gives us time to perform two - staged hearing screening tests . the most frequent risk factor was consanguinity ( 46% ) followed by mechanical ventilation ( 42% ) , very low birth weight ( 40% ) , ototoxic drugs ( 25% ) , sepsis ( 23% ) , low apgar score ( 16% ) , and hyperbilirubinemia ( 12% ) . stigmata of syndromes that are known to be associated with deafness accounted for 8% of cases in the targeted - screening groups ; 3 neonates with intestinal atresia , 2 with trachea esophageal fistula , and 3 had down 's syndrome . other less frequent factors include positive family history of hearing loss ( 2% ) and craniofacial abnormalities ( 1% ) . the most frequent risk factor for hearing loss among high - risk neonates ( group a ) was mechanical ventilation for more than 5 days ( 41/50 ) followed by birth weight less than 1500  gm ( 27/50 ) , whereas consanguinity was the most frequent risk factor for hearing loss ( 25/50 ) among neonates of the low - risk group ( group b ) followed by birth weight less than 1500  gm ( 13/50 ) . table 3 demonstrates that 19 in the high - risk group , 15 in the low - risk group , and 8 in the control group failed the teoaes bilaterally , and these 42 neonates were referred for diagnostic abr . regarding abr results , 12% of the high - risk group and 10% of the low - risk group had pchl . interestingly , 8% of neonates of the well - baby population suffered from pchl with the number needed to screen ( nns ) of 33 . in other words , to detect those 4 neonates , we have to screen approximately 132 healthy neonates . none of the risk factors were significantly related to pchl ( p > 0.05 ) . multivariate analysis of the most important risk factors for hearing loss revealed that all factors were non significantly associated with impaired abr results ( p > 0.05 ) . table 5 revealed that 11 out of the 15 children diagnosed with pchl were able to come to the follow - up visit ; 45.4% suffered from severe degree of sensorineural hearing loss ( snhl ) , 27.3% suffered from moderate degree of snhl , and 27.3% suffered from mild degree of snhl . hearing loss is twenty times more prevalent in neonates than other disorders that are routinely screened for , including hypothyroidism , phenylketonuria , and sickle cell anemia . until just a decade ago , late diagnosis was the norm , with the average age at identification of congenital hearing loss reported as 2.5 to 3 years or even later . a valuable window of opportunity for early intervention was being lost . intervention in the first 6 months of life is particularly important for speech and language development ; accordingly parents and professionals overwhelmingly prefer early diagnosis [ 2 , 5 ] .    in the current analysis , teoaes test revealed failed response in 42/150 ( 28% ) infants bilaterally . failed results were 38% , 30% , and 16% in the high - risk , low - risk , and healthy groups , respectively . the results of teoaes screening varied widely in the literature according to the characteristics of the screened population ; in egypt , el - gamal et al .   examined 90 nicu cases and reported a failure rate of 54% in the multiple risk factors group and 20% in the single risk factor group , while abdullah et al .   found that 11.8% of the screened high - risk neonates in malaysia failed the teoaes test . this prevalence of failure among the healthy neonates was far higher than that cited by korres et al .   who examined hearing in well - nursery babies with teoaes in greece and found a failure rate of 2.3% . it was assumed that failure in the first hearing screening using teoaes in this study might be secondary to external ear obstruction and/or middle ear effusion . that is why our hearing screening protocol associated teoaes with otoscopic examination and external ear cleaning or suction when necessary . additionally , two - staged teoaes test was performed in order to reduce the false positives . on the other hand , clarke et al .   suggested that screening for hearing loss in neonates should be performed 4 days after birth . therefore , failure in the neonatal hearing screening test must be understood as a possible hearing loss , and the diagnosis should be confirmed with the conventional abr three months later after complete myelination of the auditory pathway . it is very important to know the exact numbers of neonates who failed screening and actually had hearing loss confirmed in subsequent assessments . however , in the current study , diagnostic abr confirmed that bilateral pchl in 15 neonates out of the 42 ( 36% ) neonates failed teoaes screening . the reason for such high pchl rate in our study could be attributed to the characteristics of the studied group of neonates admitted to the nicu at a university hospital that is a regional excellence center and therefore provides care to highly complex cases with an expected higher prevalence of hearing loss in the population treated at this facility . attempts to screen school children for hearing loss in egypt , mostly secondary to middle ear conditions , documented a higher prevalence of hearing loss than that in the developed countries [ 1315 ] . consanguineous marriage is common in some developing communities including egypt . it could be considered as a risk factor for hearing loss because of unrecognized higher prevalence of genes responsible for heridofamilial hearing loss . in this field , mohamed et al .   disclosed a novel , functionally relevant gjb2 , a gene encoding the gap junction protein connexin 26 ( cx26 ) , mutation and defined the contribution of cx26 alterations to the hearing loss in the southern egyptian population . this finding suggests that among the snhl of unknown etiology , those of a hereditary origin should be considered . with the advances in the field of molecular genetics , new genes responsible for snhl have been identified , and the mechanisms involving nonsyndromic snhl have been explained . nevertheless , there is a consensus that the levels of pchl are greater in underdeveloped countries , with davidson et al .   estimating that snhl is twice as common . the world health organization   in its report on chronic diseases views the process from poverty to chronic diseases as  interconnected in a vicious cycle ,  as poor people have greater exposure to risks and decreased access to health services . there is some impetus for an increased effort of identification of pchl in developing countries ; trials of unhs at immunization clinics have been undertaken in nigeria and south africa and were successful in terms of coverage , but the attendance at follow - up was poor . another finding worth discussing in the current analysis is that if hearing screening was limited to the at - risk neonates , 4/50 ( 8% ) neonates from the well - baby group who had actually failed the abr test would have been missed . this finding suggests that unhs is far preferable because many hearing impaired infants do not have any risk factors . thus , unhs is strongly needed putting in mind not the cost of the screening but the cost it would be to rehabilitate a deaf - mute child . traditionally , hearing screening has been targeted to high - risk populations which represent less than 10% of births and can potentially identify between 50% and 59% of those with congenital hearing loss . in the literature , wroblewska - seniuk et al .   reported the presence of hearing impairment in 24.9% of the high - risk registers . moreover , de capua et al .   reported 11.65% failure rate of teoaes among 532 examined infants of whom only 84 were high - risk registry . although risk factors for hearing loss have been used for screening neonates in many countries worldwide , there is no consensus with regard to the importance of each of these factors and the level of relative risk . in the present study , we tried to define prospectively the risk demarcators that could predict hearing impairment in at - risk neonates . however , no significant interaction was found between any of the studied risk factors and the impaired abr results . risk factors for hearing loss are constantly refined by the jcih ; however , these factors should not be considered as the  gold standard  with the same relative importance because the situation in different countries or time periods may vary considerably . for example , a developing country like ours may use more ototoxic agents without assessing drug blood levels because of the lack of resources , whereas another developed country may not use such agents . in contrast , neonates who could have died as a result of severe prematurity and birth complications in a remote center with limited funding and equipment may very well have survived in a large nicu . therefore , continuous investigation of the relative importance of high - risk factors of hearing loss is essential to assess and refine these factors and modify accordingly current clinical practice . moreover , such studies are very useful when funding is limited and screening is inevitably targeted to the most vulnerable neonates . finally , the potential limitations inherent in this study include lack of a standard method to track children who failed screening tests and missed diagnostic abr . however , we believe that our findings provide new insights into neonatal hearing screening in a developing country like egypt . in conclusion , universal neonatal screening for congenital hearing loss would detect more cases than targeted , risk - based screening , allowing for early intervention . designing hearing screening policy , refining risk factors , and implementing follow - up and treatment protocols
aim . to compare 
 targeted neonatal hearing screening ( tnhs ) and universal neonatal hearing screening ( unhs ) since many developing countries , including egypt , implement selective screening for high - risk neonates . 
 methods . 
 150 neonates were assessed ; 50 full terms consecutively admitted to the well - baby nursery and 100 neonates consecutively admitted to neonatal intensive care unit ( nicu ) , ain shams university . 
 patients were further subdivided into high - risk group which included 50 neonates with multiple risk factors for hearing loss and low risk group which included 50 neonates with only one risk factor . 
 transient evoked otoacoustic emissions ( teoaes ) were used for hearing screening . 
 auditory brain response ( abr ) was performed 3 months later for failed teoaes . 
 results . 
 the most frequent risk factor was consanguinity ( 46% ) . in the well - baby population , 
 16% failed teoaes . in the nicu , 
 30% of the low risk and 38% of the high risk groups failed teoaes . 
 regarding abr , failed results were 12% , 10% , and 8% in the high - risk , low - risk , and healthy groups , respectively . 
 conclusion . 
 the use of tnhs would have missed 8% of neonates from the well - baby group who actually had pchl ( permanent congenital hearing loss ) . 
 the use of unhs would identify all cases with pchl , allowing for early intervention and follow - up .