Rare disease surveillance: An international perspective.

BACKGROUND The International Network of Paediatric Surveillance Units (INoPSU) was established in 1998 and met formally for the first time in Ottawa, Ontario in June 2000. OBJECTIVES To document the methodology and activities of existing national paediatric surveillance units; the formation of INoPSU; the diseases studied by INoPSU members; and the impact of such studies on education, public health and paediatric practice. METHODS Directors of paediatric surveillance units in Australia, Britain, Canada, Germany, the Netherlands, Latvia, Malaysia, Papua New Guinea, New Zealand and Switzerland were asked to provide information on each unit's affiliations, funding and staffing; the method of case ascertainment, the mailing list and response rates; and diseases studied. Original articles that reported data derived from units were identified by a search of an electronic database (MEDLINE), and additional information was obtained from units' annual reports. RESULTS Worldwide, 10 units (established from 1986 to 1997), use active national surveillance of more than 8500 clinicians each month to identify cases of rare or uncommon diseases in a childhood population (younger than 15 years of age) of over 47 million (monthly response rate 73% to 98%). By January 1999, units had initiated 147 studies on 103 different conditions, and 63 studies were completed. CONCLUSION INoPSU enhances collaboration among units from four continents, providing a unique opportunity for simultaneous cross-sectional studies of rare diseases in populations with diverse geographical and ethnic characteristics. It facilitates the sharing of ideas regarding current methodology, ethics, the most appropriate means of evaluating units and their potential application.