The need for a population survey

At the Third Triennial International PWS Conference in Venice in 1998, the scientists present agreed that a large population prevalence study of PWS was needed for two main reasons. First, the two earlier population surveys had not been large enough to produce reliable estimates and, in the case of one of them that surveyed people aged 0–25 years, had not been comprehensive. Moreover, neither of these two studies used genetic criteria for the diagnosis of PWS and therefore the prevalences were very likely to be over-estimates. A larger population study, using established clinical diagnostic criteria together with recently agreed genetic diagnostic techniques, would therefore provide more accurate population prevalence and birth incidence figures. Second, the possibility of sampling bias could not be ruled out where conflicting findings had been obtained in different studies that used groups of people with PWS who were ascertained via specialist clinics or who had volunteered. It was strongly suspected that such a bias was an explanation for at least some of the contradictions. That is, in these conflicting studies, the groups of people with PWS who were included were probably not representative of the PWS population more generally. A new population survey, with genetic confirmation of the diagnosis, would both provide a representative sample of people with PWS to help with future research and more accurate prevalence data on which to determine service requirements.