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Objectives: Etiological diagnosis of hearing impairment is of great importance to ensure early and adequate management. Even after thorough history taking, clinical and audiometric evaluation, the cause of hearing loss remains unclear in a majority of patients. Further examinations can imply imaging, ophthalmologic investigations, laboratory tests, electrocardiography and genetic testing. Lately, the latter has taken an increasingly prominent place within this diagnostic work-up. However, clear guidelines about optimal implementation and sequence of these tests are required., Methods: Records of patients who visited the consultation for otogenetics at Ghent University Hospital (Belgium) during the period 2006-2012 were retrospectively reviewed. In order to optimize the etiological-diagnostic work-up of unidentified hearing loss, application patterns and results of various diagnostic tests, audiometric and etiological data of each patient were collected and analyzed., Results: Data of 191 patients were analyzed. In 81.2% of the patients, a cause of hearing loss could be determined or suspected. In total, 65.4% had a (presumably) genetic etiology, with connexin 26 (GJB2) mutations as the leading cause. Inquiry of risk factors, associated with congenital hearing loss, and pedigree analysis were found to have the highest diagnostic gain (61.3% and 41.8%). Connexin 26 gene mutations were only present in bilateral hearing impairment, whereas CT abnormalities were related to unilateral (P=0.003), profound (P<0.001) hearing loss. An enlarged vestibular aqueduct was present in 42.9% of all CT abnormalities. Ophthalmologic anomalies were detected in 35.7% of the studied patients., Conclusions: A sequential approach for the etiological diagnosis of unidentified hearing loss could determine or suggest a cause in more than 80% of patients. The approach may vary based on the presenting phenotype., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)