ASD Prevalence Study across Europe: Cross Sectional Study Design in Six European Countries

Background: Although ASD prevalence studies have been carried out worldwide, the lack of mechanisms to obtain consistent and reliable information about ASD trends across European countries has been an important obstacle for making policy decisions at both the European Union (EU) and individual national levels. The Autism Spectrum Disorder in the European Union (ASDEU – http://asdeu.eu) project is a multi-site European collaboration with several objectives including estimation of ASD prevalence and developing harmonized prevalence strategies.

Objectives: The presentation will describe preliminary results of the harmonized multi-site field survey strategy aimed at children ages 7-9 years old. It will reflect upon lessons learned regarding the field survey methods and their practical implementation in real-world settings.

Methods: Eight ASDEU partners (Austria, Bulgaria, Ireland, Italy, Poland, Portugal, Romania, Spain) are conducting the prevalence field survey based on school screening methods in defined geographic catchment areas. In general, the field strategy first involves a “Teacher Nomination Form” (TNF) for teachers to nominate possible ASD cases in their classes, followed by completion of the SCQ by parents (of teacher-nominated children or all children in the classroom), followed by a clinical evaluation of nominated children using the ADOS-G and other tools; two countries only used the SCQ in the screening process. The presentation will focus on 6 countries (Spain, Portugal, Italy, Romania, Poland, Austria) with most progress to date. The six countries provided data from 9 different catchment areas; 4 countries used both the TNF and SCQ and 2 used the SCQ only. Each country implemented minor variations in the screening approach to comply with ethical committee or school approvals; to manage the relationship between researchers, teachers and school authorities; and to manage the timing of parental consent.

Results: Portugal, Poland, Austria and Romania screened children in both special needs and regular schools; in Spain and Italy special needs children are integrated into regular schools. Portugal, Italy, Austria and Romania randomly selected schools in their study catchment areas; Poland randomly selected schools in one study area and all schools in 3 areas; Spain included all schools in its study area. The number of selected schools ranged from 47-217 per country; the participation rate of schools across countries ranged from 49%-100%; 252-498 teachers per country contributed to the first screening phase of 5,951-13,335 students per country applying the TNF (Spain, Portugal, Poland and Romania) and 10,872 and 13,628 students from Austria and Italy, respectively, only using the SCQ. From 1.3% to 3.0% of children were TNF-nominated in Spain, Portugal, Poland, and Romania. The clinical assessment phase of nominated children is ongoing.

Conclusions: This is the first comprehensive European action to estimate ASD prevalence. Use of the TNF and SCQ as school-based screening tools suggests the TNF is feasible to administer, well received, and provides greater coverage of the target population with lower implementation costs than the SCQ. Analysis will compare prevalence estimates derived from the TNF versus SCQ screening tools and results will inform the development of future ASD prevalence strategies across EU countries.