New opinions on DTC genetic testing

8 October 2009

The brave new world of consumer genomics has attracted enormous interest both in the popular press and amongst the scientific and medical establishment. Opinions vary widely about the validity and utility of these tests, and the extent to which such services should be regulated (see previous news). The internationally renowned journal Nature has now entered the foray with an editorial [Nature (2009) 461: 697-8] and an opinion piece [Ng PC et al. Nature (2009) 461:724-6] about direct-to-consumer (DTC) genetic testing companies.
The editorial criticises the "Framework of Principles for direct-to-consumer genetic testing services developed by the Human Genetics Commission (HGC), which is currently in draft form and open for public consultation (see previous news). It states that “the value of the tests remains debatable, which is why the industry needs a strong set of quality standards and codes of conduct to protect both its consumers and its own credibility”. Whilst this is unquestionably true, the level of regulation required to achieve appropriate standards which are in-line with other health-related tests available to the public remains contentious. Nature suggests that ultimately government regulators may need to be involved in order to adequately protect consumers.
The opinion piece analyses the results for five individuals from two DTC genetics companies, both based in California: 23andMe and Navigenics. Although the concordance between the companies in terms of the genotype data (i.e. the analytical validity) was high, for the seven diseases analysed, less than 50% of the predictions from the two companies agreed across all five individuals. This is not a new discovery, nor is it particularly surprising given the different methods and genetic variants used by the two companies (see Genetic Future blog), but it nonetheless raises important issues about the clinical validity and any possible utility that could derive from the information as it stands. The authors highlight several important areas where further research by the genetics community is urgently needed, including monitoring behavioural outcomes following testing, prospective trials to determine the predictive value of multivariate genetic tests, and determining the underlying causal variants so that genetic sequencing (rather than SNP genotyping) can be used. In addition, the authors also make some useful recommendations specifically directed at DTC companies:
  1. Report the genetic contribution for the markers tested, not just the role of genetics versus environment
  2. Focus on high-risk predictions, to target lifestyle changes which could make a difference
  3. Directly genotype risk markers, rather than choosing surrogate markers (which are in linkage disequilibrium with those in the published literature); although this practice is commonplace in population research, it may not be valid for individuals
  4. Test pharmacogenomic markers, to reduce potential adverse drug reactions
  5. Agree on strong marker effects, and hence use the same genetic variants in their predictions
Comment: These recommendations are useful, and would certainly improve the consistency and reliability of genomic risk profiling services. The first recommendation – to report on the genetic contribution made to the disease by the markers tested – would undoubtedly be a valuable addition to the information provided by the companies, and improve an individual’s ability to correctly interpret the significance of their results. However, the other four may be overly demanding compared with requirements for other sorts of commercial health tests and services. Whilst ensuring a high level of accuracy, reliability, validity and utility is vitally important within a state (or third party) funded health system, in order to achieve the equitable distribution of limited funds, the same is not necessarily true for the consumer market.
Outside of the genetics field, companies can provide health-related information without being told what diseases they should focus on, as it is assumed that market forces will weed out the irrelevant tests; manufacturers are also at liberty to choose what biomarker to measure, so long as they can provide evidence that it is linked to their claims. Moreover, so long as the test device itself poses no direct physical harm to the consumer – which is certainly the case for most DTC genetic testing services – individual citizens are free to choose what to buy and how to react to their results. As the final paragraph of the editorial emphasises, regulators need to “proceed with care” and not apply more exacting standards to these tests simply because they are based on DNA.