190 Utility of molecular testing for RP—Mezer et al Utility of molecular testing for related retinal dystrophies Eedy Mezer, MD; Joanne Sutherland, MSc; Stephanie L. Goei, MD; Elise Héon, MD, FRCSC; Alex V. Levin, MD, MHSc, FRCSC ABSTRACT • RÉSUMÉ Background: The purpose of this study was to describe our experience with the clinical effects of molecular genetic testing for retinitis pigmentosa (RP) and related retinal dystrophies. Methods: Chart review of 303 consecutive patients with retinal dystrophies was done when blood was sent for molecular genetic testing between 1993 and 2001. Phenotype information was retrieved for patients with identified mutations. The yield of positive and clinically useful results was assessed. Results: Participants comprised 35 patients with Leber congenital amaurosis, 18 with Usher syndrome, and 250 with isolated RP or other retinal dystrophies. Of these 303 participants, 203 (67%) received positive or negative results of molecular testing for an average of 2.7 genes. Positive results were available in 19 patients after an average time interval of 38 ± 22 months (median 33 months, range 1–89 months). No results were received for 84 (28%) patients. In 16 (5%) cases, patients received partial results.Only 19 (6%) patients were found to have sequence changes in RHO, RDS, CRB1, or USH2A, 2 of which were thought to be disease-causing. Only 2 sequence changes were previously documented mutations,but several other novel changes were suspected to be disease-causing mutations also. Interpretation: Molecular testing was helpful only in the minority of cases, largely because of a lack of availability, as well as the complexity of the molecular genetics of RP. Improvements in funding, infrastructure, and molecular knowledge will be necessary to improve the transformation of molecular genetic testing into a clinically relevant bedside tool. Contexte : Cette étude a pour objet de décrire notre expérience concernant le résultat clinique des analyses génétiques moléculaires de la rétinite pigmentaire (RP) et des dystrophies rétiniennes qui lui sont apparentées. Méthodes : L’examen des dossiers de 303 patients consécutifs a été effectué au moment où le sang était envoyé à l’analyse génétique moléculaire entre 1993 et 2001. L’information phénotypique a été réunie pour les patients qui avaient des mutations identifiées. Les résultats positifs et cliniquement utiles ont été évalués. From the Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, University of Toronto, Toronto, Ont. Dr. Mezer is now with the Alberto Moscona Department of Ophthal- mology, Rambam Health Care Campus, Haifa, Israel Presented in part to the International Society for Genetic Eye Disease in Paris May 20, 2003 Originally received Feb. 24, 2005 Accepted for publication Jan. 20, 2006 Correspondence to: Dr. Alex V. Levin, Department of Ophthalmology, M158, The Hospital for Sick Children, 555 University Ave., Toronto ON M5G 1X8; fax (416) 813-6261; alex.levin@sickkids.ca This article has been peer-reviewed. Can J Ophthalmol 2006;41:190–6