Genetic study of Diabetic Retinopathy: recruitment methodology and analysis of baseline characteristics
Fogarty, Rhys Daniel
Chang, John H
Hewitt, Alex W
Burdon, Kathryn Penelope
Craig, Jamie E
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BACKGROUND: Diabetic retinopathy (DR) is a blinding disease of increasing prevalence, caused by a complex interplay of genetic and environmental factors. Here we describe the patient recruitment methodology, case and control definitions, and clinical characteristics of a study sample to be used for genome-wide association (GWAS) analysis to detect genetic risk variants of DR. METHODS: 1669 participants with either type 1 (T1) or type 2 (T2) diabetes mellitus (DM) aged 18 to 95 years were recruited in Australian hospital clinics. Individuals with T2DM had disease duration of at least 5 years, and were taking oral hypoglycemic medication, and/or insulin therapy. Participants underwent ophthalmic examination. Medical history and biochemistry results were collected. Venous blood was obtained for genetic analysis. RESULTS: 683 diabetic cases (178 T1DM and 505 T2DM participants) with sight-threatening DR, defined as severe non-proliferative DR (NPDR), proliferative DR (PDR) or diabetic macular edema (DME) were included in this analysis. 812 individuals with DM but no DR or minimal NPDR were recruited as controls (191 with T1DM and 621 with T2DM). The presence of sight-threatening DR was significantly correlated with DM duration, hypertension, nephropathy, neuropathy, HbA1C and BMI. DME was associated with T2DM (p<0.001), whereas PDR was associated with T1DM (p<0.001). CONCLUSIONS: Adoption of a case-control study design involving extremes of the DR phenotype makes this a suitable cohort, for a well-powered GWAS to detect genetic risk variants for DR.
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