Time after birth in relation to failure rate in newborn hearing screening

To verify and correlate the rate of failure in the newborn hearing screening in relation to the time of life of the newborn when the procedure is carried out.

The study focused on babies born on a maternity, from October/2010 to March/2011. Newborns possessing one or more risk indicators for auditory impairment as described by the JCIH, 2007 or with time of life longer than 60 h were excluded. An automated transient evoked otoacoustic emission equipment was used. The "pass" criterion adopted was: signal to noise ratio greater than 6dB and a minimum signal level of -5dbNPS in at least three frequencies. Babies were divided in three groups: GI: fewer than 24 h old, GII: between 24 and 36 h, and GIII: more than 36 h.

890 babies were included, 52% male and 48% female. Of all newborns, 70% passed the test and 30% failed. Regarding gender, 30% female and 31% male failed the test. 35% of the newborns were in GI, 53% in GII and 12% in GIII. Comparing the three groups simultaneously, we conclude that there is evidence of differences between them (P value <0.001). When compared two by two, we conclude that the distributions of GII and GIII may be considered the same (P=0.443), but both are different from GI (P<0.001). We noticed that in GII and GIII, the proportion of patients who presented de "pass" result is much higher than that of patients who presented this result in GI. The result of logistic regression shows that with the passing of each hour after birth, a newborn's chance of failing the test decreases by 5%.

We have concluded that the failure rate in the newborn hearing screening was much higher in the newborns screened within 24 h from birth, deviating statistically from the newborns screened between 24 and 36 h. There was no statistically significant difference between the latter two time brackets.