Genome-wide studies have recently identified many new variants associated with common diseases. Findings point mainly to sets of variants with modest effects, with many more markers still to be discovered. Some variants are shedding new light on disease mechanisms and on previously unsuspected parts of the genome. Much more work is needed, however, to define the clinical relevance and value to patients of testing for these new genetic markers. It is worrying that in the absence of this knowledge, commercial genetic testing services are being marketed directly to the public. In this paper we describe key findings from the new genome-wide association studies; draw attention to the currently weak regulatory systems, particularly in Europe; and argue the case for improved evaluation, greater transparency, and better regulation, so that the new genetic tests can be used in a safe and informed way.

Environmental factors are major contributors to the development of most common diseases. However, conditions including myocardial infarction, type 2 diabetes, asthma, and even the ageing process itself are influenced by inherited variations in DNA sequence.1 The most common DNA variant is the substitution of a single base pair: when these occur at a population prevalence of 1% or more; they are termed single nucleotide polymorphisms or SNPs (pronounced “snips”). More complex variants exist, including deletions, insertions, and copy number variations, but most of the recent work on the genetics of common diseases has focused on SNPs.

In tandem with the sequencing of the human genome, extraordinary advances have occurred in the technology for determining the status of SNPs. The original wet laboratory techniques gave way to robotic systems and then to miniaturisation. The latest format has test probes arrayed on the surface of a …