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This article discusses the role of genetics in macular degeneration and the limitations of current genetic testing methods. It highlights the need for further research and clinical trials before routine genetic testing is recommended. The standard clinical examination is currently more reliable in detecting treatable disease.
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Genetic Testing for Macular Degeneration Edwin M. Stone, M.D., Ph.D. The Howard Hughes Medical Institute The University of Iowa Institute for Vision Research
US Population over 75 years(will increase 44% by 2025) 19 million in 2012 27 million in 2025 From the US Census Bureau
AMD is Genetic • More than 50% of all AMD is attributable to genetic factors • Several genes, especially CFH and ARMS2, have been significantly associated with the development of AMD
The Role of Genetics • Elucidate molecular mechanisms. • Create in vitro and animal models. • Enable novel mechanism-specific presymptomatic therapies. • Identify patient populations for clinical trials of these therapies.
Task Force Recommendation Avoid routine genetic testing for genetically complex disorders like age-related macular degeneration . . . until specific treatment or surveillance strategies have been shown in one or more published clinical trials to be of benefit to individuals with specific disease-associated genotypes. In the meantime, confine the genotyping of such patients to research studies. Ophthalmology. 2012 Nov;119(11):2408-10
Current AMD genetic tests have not been shown to improve clinical outcome. • Less sensitive and specific than clinicians. • No mechanism-specific therapy available. • None of the tests can reliably distinguish between dry AMD and CNV.
ARMS2 Normal vs AMD, p = 1.1 x 10-23 Dry vs CNV, p = 0.29 (NS) n = 646 AMD pts, 305 controls High Risk Het Low Risk
Complement Factor H Normal vs AMD, p = 3.8 x 10-19 Dry vs CNV, p = 0.36 (NS) n = 646 AMD pts, 305 controls High Risk Het Low Risk
PIIR Study(Pepose Institute, University of Missouri, Illinois Retina)N. Holekamp, A. Almony, M. MacCumber • 103 subjects were tested for free by two commercial labs: Arctic Dx (Macula Risk®) and Sequenom CMM (RetnaGene™ AMD) • 97 subjects had sufficient genotypic and clinical information for comparison • 17/97 were normal controls (avg age 76.9 yrs) • 33/97 had dry AMD (avg age 79.3 yrs) • 47/97 had CNV (avg age 79.3 years)
Genotyping Errors • Arctic Dx failed to detect the CFH H3 haplotype in any patients (this haplotype is present in about 30% of the population). • There were no detectable genotyping errors in the data provided by Sequenom.
Risk Comparison Method • Patients were assigned a risk rank from 1 (mildest) to 97 (most severe) based on the risk score assigned to them from each company. • These risk ranks were compared to each other and to the clinical phenotype assigned by the investigators.
Conclusions • Avoid routine genetic testing for AMD until specific treatments have been shown in clinical trials to be of benefit to individuals with specific disease-associated genotypes. • For now, the standard clinical examination is more sensitive and specific for detecting treatable disease than any genetic test.