Genetic testing for rare disorders: managing expectations and costs

Abstract

Rare genetic diseases have issues that are unique from the issues of testing for genetic factors related to common genetic diseases that largely result from the strength of the genetic factors and their high penetrance. Although only affecting 5% or so of a population, the strength of the genetic factors are such that their intended uses are very broad. We are currently offering genetic tests in over 1500 genes for rare diseases with more being developed every week. Not only are the tests for these conditions useful in a diagnostic and family based setting but they can also be useful in targeted screening or general population screening when particular criteria are met that make them cost-effective in a healthcare setting. Most rare genetic disease tests lack the knowledge base to make then useful outside of diagnostic and family settings at the current time but some have made the leap to public health application. Many systems have developed that recognise the difficulty in developing the statistical power that is possible in more common diseases and their associated interventions. Programs such as the Orphan Drug Act of the US Food and Drug Administration recognise the statistical hurdles and shift the focus towards post-market surveillance in order that these tests and therapeutics can be made available to the public. As such, much improved systems will be necessary through which the evidence about the clinical histories of diseases, whether treated directly or symptomatically, can be collected. The international nature of genetic diseases and the benefit to countries with multicultural populations are such that it is an area in which international collaboration is possible and of potential benefit to all.