Molecular diagnosis of non-syndromic hearing loss patients using a stepwise approach

Hearing loss is one of the most common birth disorders in humans, with an estimated prevalence of 1-3 in every 1000 newborns. This study investigates the molecular etiology of a hearing loss cohort using a stepwise strategy to effectively diagnose patients and address the challenges posed by the genetic heterogeneity and variable mutation spectrum of hearing loss. In order to target known pathogenic variants, multiplex PCR plus next-generation sequencing was applied in the first step; patients which did not receive a diagnosis from this were further referred for exome sequencing. A total of 92 unrelated patients with nonsyndromic hearing loss were enrolled in the study. In total, 64% (59/92) of the patients were molecularly diagnosed, 44 of them in the first step by multiplex PCR plus sequencing. Exome sequencing resulted in eleven diagnoses (23%, 11/48) and four probable diagnoses (8%, 4/48) among the 48 patients who were not diagnosed in the first step. The rate of secondary findings from exome sequencing in our cohort was 3% (2/58). This research presents a molecular diagnosis spectrum of 92 non-syndromic hearing loss patients and demonstrates the benefits of using a stepwise diagnostic approach in the genetic testing of nonsyndromic hearing loss.