Test may skew age-related macular degeneration risks in blacks

March 1, 2012

Genetic testing for age-related macular degeneration grew a little more complicated with new research suggesting that these tests may not accurately predict risk in non-Hispanic blacks.

Genetic testing for age-related macular degeneration (AMD) grew a little more complicated with new research suggesting that these tests may not acurately predict risk in non-Hispanic blacks, but Optometric Retina Society President Larry Alexander, OD, FAAO, said genetic testing still has a useful role in AMD, although clinicians need to fully understand the test and its limitations.

The investigators examined randomly selected fundus photographs using the Wisconsin Age-Related Maculopathy Grading System. They found a positive association between the ARMS2 A69S gene variant and AMD in non-Hispanic white and Mexican-American participants, but an inverse relationship from the same variant in non-Hispanic blacks.

"Regardless of the reason, if this inverse association in non-Hispanic black individuals is confirmed, genetic tests that naïvely incorporate ARMS2 A69S without considering ancestry will consistently give incorrect results to non-Hispanic black individuals," the authors wrote. "Falsely inflated risk estimates may lead to unnecessary follow-up care, increasing both cost and anxiety for these patients, while falsely decreased estimates may decrease vigilance in monitoring eye health."

The researchers stated they did not know why the predictive value differs among racial and ethnic groups. "As our results highlight, predictive genetic testing for complex diseases faces many challenges," they wrote. "Until we fully understand how a particular genetic variant acts on disease susceptibility, great care must be taken when translating genetic tests from one race-ethnicity to another."

What it means to ODs

"Not everyone with macular drusen needs this test," Dr. Alexander said. "It can't be used in a vacuum." But he also noted that, in many cases, the initial diagnosis of AMD doesn't occur until a patient suffers vision loss in an eye, and that testing can provide the opportunity to begin earlier treatment with appropriate vitamins and changing behaviors considered risk factors for AMD.

"One of the benefits of the test is that it gives you a chance to save vision in the first eye and intervene before it's a [critical] problem," he said.

He still believes genetic testing has a place in the optometric armamentarium. Clinicians need to consider patients' family history of AMD, ethnicity, the presence of other risk factors, and cost to decide with the patient whether to proceed with a test.