Values of BERA in newborns and its association with latent intrauterine iron deficiency and neonatal TSH

Abstract

Adequate hormonal and nutritional levels during fetal development and early postnatal life are critical to the proper development of the central nervous system. It is a period of high sensitivity to deficiencies of substrates necessary for neurodevelopment. There is evidence that iron deficiency and congenital hypothyroidism are diseases capable of impairing cognitive and behavioral development of the affected subject, especially when not detected and treated early. In both conditions, the development of auditory function and its myelination suffer damages that can be detected early through EOAE (Evoked Otoacoustic Emissions) and BERA (Brainstem Evoked Response Audiometry) tests performed in the first days of life. The present study aims to analyze the relationship between latent iron deficiency in the newborn and TSH values from neonatal screening with myelination of the newborn auditory nerve (as measured by BERA), furthermore contributing to the local epidemiological study and the adequate referral to the children with detected hearing loss. This study is transversal, quantitative and will be developed at the Santa Casa de Misericórdia Hospital's Maternity in São Carlos, on a convenience sample. The expected sample of the project is 1200 RNs, aiming at a target population of 60 RNs with latent iron deficiency. The umbilical cord blood sample for determination of ferritin and hematocrit levels will be collected soon after birth. The hematocrit will be measured after centrifugation in an appropriate tube, under standard conditions, by the method of Wintrobe et al (1987). Ferritin dosing will be performed using a solid phase chemiluminescent immunometric enzyme assay (IMMULITE/IMMULITE 1000 FERRITIN - Siemens Healthcare Diagnostics UK). The thyroid stimulating hormone (TSH) data will be collected from the results of neonatal screening, in the municipal epidemiological surveillance department. The BERA and EOAE exams will be performed by the same professional who will not have prior access to blood tests results and will be performed between 01 and 28 days postpartum (neonatal period). EOAE will be performed in "pass or fail" screening mode and BERA will be in diagnostic mode. BERA will be measured using a sound stimulus of 80dBNA at a rate of 27.7 clicks/second (HOOD STANDARDIZATION- 1998). Data will be presented as mean ± standard deviation and the level of significance adopted will be 5%. The statistical significance of the differences between the variables will be determined by the non parametric T test for comparison between two variables and by the chi-square test for categorical data. The Spearman test will be used to evaluate the degree of correlation between the variables. (AU)