Methodology of a multistate study of congenital hearing loss: preliminary data from Utah newborn screening

Abstract

A multistate Centers for Disease Control and Prevention (CDC) study was designed to investigate the etiology of congenital hearing loss in infants ascertained through state-mandated hearing screening or early hearing loss detection and intervention (EHDI) programs. At least 50% of permanent childhood-onset hearing loss is due to genetic causes, and approximately 20% of all infants with congenital hearing loss have mutations in the GJB2 gene. Another 1% of childhood hearing loss is due to mitochondrial DNA (mtDNA) mutations. The specific aims of this study are to 1) classify the etiology of congenital hearing loss in infants by doing prospective genetic evaluations of all newborns with permanent hearing loss from defined geographic areas, 2) determine the frequency of mutations in GJB2 and two common mitochondrial mutations in these populations, and 3) establish a model infrastructure linking genetic services to statewide EHDI programs. As of April 2003, Utah is the only center evaluating patients. Study subjects identified through the Utah Department of Health EHDI program are contacted by letter and offered a comprehensive medical genetics evaluation with DNA testing for GJB2 and mitochondrial mutations A1555G and A7445G. To date, 25 probands and their immediate family members have been evaluated. We have identified 20 cases with nonsyndromic hearing loss (7 multiplex and 13 simplex), 4 with syndromic hearing loss, and 1 with presumed cytomegalovirus (CMV)-induced hearing loss. Six of 19 (32%) nonsyndromic cases with sensorineural hearing loss have mutations of one or both alleles of the GJB2 gene, and 21% are homozygous or compound heterozygotes for the 35delG mutation. No A1555G or A7445G mtDNA mutations have been found. Data reported to date include only children born in Utah, but EHDI programs in Hawaii, Rhode Island, and designated areas of Georgia have begun enrolling children in what is now a multistate collaborative study. This is the first comprehensive investigation to determine the etiology of hearing loss from populations ascertained through EHDI programs. The results of this study will facilitate the incorporation of genetic services into EHDI programs.