Deafness test is placed first

The testing method for diagnosing deafness of genetic origin, adapted by doctor Edi Lúcia Sartorato – already covered in previous editions of Jornal da Unicamp – was ranked first in the State Governor's Award in 2001. And it is about to become mandatory in hospitals and maternity wards, which depends on the approval in the São Paulo Legislative Assembly of a bill authored by deputy Vitor Sapienza (PPS).

The merit of the test, which was patented for safety reasons (so that it can be applied correctly), is the ease of diagnosis. “It was done in another, more sophisticated way, and we achieved a faster, more practical and cheaper method”, explains Edi, researcher at the Center for Molecular Biology and Genetic Engineering (CBMEG) at Unicamp.

Using a piece of absorbent paper – which can be the usual paper for blood tests or even a coffee filter –, the blood is collected and the test is performed with accurate results. The project financed by Fapesp began in 1999, following the observation that one in a thousand children is born or becomes deaf in developed countries, with 60% of cases of genetic origin. With the advancement of research in this area, the importance of studying mutations in the connexin 26 gene became evident, specifically a mutation called 35delG (inherited from father or mother), the most frequent mutation observed to date in Caucasians. It is estimated that it affects one in every 5.000 Brazilian children.

Blood collected on paper is examined by a reaction using a device called a thermocycler, which allows 43 simultaneous tests. It can be done together with the heel prick test, which currently allows up to 80 pathologies to be identified in newborns. The greatest importance is in early detection of the mutation. “A child may be born hearing, but will inevitably become deaf. There are cases in which the disability only manifests itself in adulthood, but there are no people known who have the mutation and do not become deaf”, says Edi.

Planning – In deafness of genetic origin, there is no cure. “But we can work so that the child learns to speak before completely losing their hearing. By detecting the problem during the main period of brain development, we can act towards its inclusion in the social environment”, highlights the researcher. In Brazil, disability is noticed at three years of age, on average. “That's when the mother starts to worry because the child doesn't speak. During this period, the couple may have had another baby, with the same genetic problem, as the chance of another deaf child recurring in the family is 25%. With early detection, parents would have the chance of family planning based on the risks”, ponders Edi.

A deaf child can perfectly well attend a hearing school, if they are prepared for it and can speak. “Ideally, the diagnosis should be made up to three months of age and rehabilitation intervention up to six months. The exam serves as a relief for the mother, who, by knowing the cause of her child's disability, frees herself from guilt,” she explains. Anyone can check, using this method, whether they carry the mutation: both people with deafness who are unaware of the cause, and individuals with this family history.

The mutation is most common in Europe, where it is present in one in 51 individuals; in Italy, the proportion is one in 32. Deafness occurs in 25% of descendants of fathers and mothers who have the mutation, due to the combination of pairs of genes. As a large part of the Brazilian population is of European descent, a survey is being carried out to detect the exact incidence of carriers of the 35delG mutation in the country.

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