Impact of new screening technologies: should we screen and does phenotype influence this decision?

The early detection offered by newborn screening for phenylketonuria clearly demonstrates the benefits for patients with inherited metabolic disorders of well organised screening programmes. It is therefore perhaps surprising that 20 years after the introduction of electrospray MS/MS methods to support expanded newborn screening that considerable international variation in practice, not linked to economic factors, exists. It is likely that the commonly used criteria to assess the suitability of a disorder for screening need to be re-appraised as they apply to rare disorders. In addition, national differences in the pattern of policy making may influence the strategy adopted and these different approaches need to be scrutinised more closely. Despite this contextual variation a number of real issues do need to be addressed as the range of conditions included in screening programmes continues to increase. These include the need for well organised outcome studies based upon agreed case definitions and comparable treatment regimens; the need for appropriate information for parents to support them before and during the screening odyssey; an improved understanding of the impact of false positive results and in particular a clearer understanding of the way in which some of the problems resulting from false positive results can be avoided or ameliorated; the challenge offered by mild or atypical screen positive cases and the consequent design of proportionate treatment options. A thorough understanding of the genetic, biochemical and clinical features of screen positive cases supported by effective international outcome studies is required to optimise both screening and treatment strategies.