Awh versus the NEI

In an era where you can pay US$1000 to get your entire genome sequenced, it doesn’t seem like too much of a stretch to compare your genetic data against the list of drugs your physician’s prescribed to you. Most pharmacogenomic testing pertains to drug metabolism (is your liver converting enough pro-drug to drug – or too much?) but it may now apply to the dietary supplements people take to stave off the development of AMD (1) – albeit with a hefty dose of controversy (2). Carl Awh is a retinal specialist in a private practice in Nashville, TN, who has access to the Age-Related Eye Disease Study (AREDS) dataset, and the genetic material of many of the patients that participated in the trial. The AREDS trial originally showed that the development of AMD is delayed in people who take certain nutritional supplements – Vitamins C, E, β-carotene, zinc and copper – leading to the National Eye Institute (NEI) to recommend the trial formulation in patients with moderate AMD.

There are a number of genes that, if mutated, increase the risk of a patient developing early AMD; two particularly prominent ones are complement factor H (CFH), and age-related maculopathy susceptibility-2 (ARMS-2). Awh et al’s pharmacogenomic analysis of the AREDS data suggested that certain polymorphisms (risk alleles) in either of those genes could lead to a reduction in the benefit patients received from AREDS supplementation (3). At the 32nd Annual Meeting of the American Society of Retina Specialists, he took this further, stating that patients with one or more CFH risk alleles taking Zinc-containing supplements might actually experience an increase in the rate of AMD progression, rather than a reduction. Awh’s also a prominent proponent of genetic testing – he believes that genotype-directed dietary supplementation for patients with AMD should be performed regularly (3). Not everyone agrees with his interpretation. The NEI performed similar analyses on the same dataset and reaches the opposite conclusion – they found no statistically significant differences in AREDS supplementation benefit across all of the CFH and ARMS2 genotypes examined. They conclude that currently, genotyping in AMD is of no benefit for the management of nutritional supplementation in patients with AMD (4). The NEI authors accounted for the differences in their respective results: they had a larger sample size in their study than Awh and colleages (1237 vs 995).