Ability and Disability in Autism Spectrum Disorder: A Systematic Literature Review Employing the International Classification of Functioning, Disability and Health-Children and Youth Version (ICF-CY)

Background:  The International Classification of Functioning, Disability and Health (ICF) was initiated by the World Health Organization (WHO) in 2001 to provide a comprehensive and an universally accepted framework for the description of health-related functioning. The  ICF is based on an integrative biopsychosocial model of functioning and comprises over 1,400 categories related to various components of health, specifically; body functions (physiological functions of body systems), body structures (anatomical parts of the body), activities (execution of tasks), participation (involvement in a life situation) and environmental factors (physical, social and attitudinal environment of people). To facilitate the practical use of this comprehensive framework, so called ICF Core Sets have been developed for several health conditions. These are shortlists of generally-agreed-upon ICF categories that capture the aspects of functioning that are pertinent to individuals with a certain health condition. In order to facilitate the use of the ICF in ASD, the Karolinska Institutet Center of Neurodevelopmental Disorders (KIND) has initiated the process of developing ICF Core Sets for ASD, which are lists of generally-agreed-upon ICF categories that are pertinent to individuals with a certain health condition.

Objectives:  The objective was to use a systematic review approach to identify, number, and link functional ability and disability concepts used in the scientific ASD literature to the nomenclature of the ICF-CY (Children and Youth version of the ICF, covering the life span). 

Methods:  Systematic searches on outcome studies of ASD were carried out in Medline/PubMed, PsycINFO, ERIC and Cinahl, and relevant functional ability and disability concepts extracted from the included studies. These concepts were then linked to the ICF-CY by two independent researchers using a standardized linking procedure. Since the search yielded large number of studies, samples were analyzed until no more new ICF-CY categories were identified. 

Results:  Seventy-one studies were included in the final analysis and 2475 meaningful concepts contained in these studies were linked to 146 ICF-CY categories. To restrict the results to those categories that are most relevant to ASD, only those that were identified in at least 5 % of the studies were reported. This left 99 categories for the final results, of which 63 were related to Activities and Participation, 28 were related to Body functions, and 8 were related to Environmental factors. The five most frequently identified categories were basic interpersonal interactions (51%), emotional functions (49%), complex interpersonal interactions (48%), attention functions (44%), and mental functions of language (44%). 

Conclusions:  The broad variety of ICF-CY categories identified in this study reflects the heterogeneity of functional alterations found in ASD – both with respect to disability and exceptionality – and underlines the potential value of the ICF-CY as a framework to capture an individual’s functioning in all dimensions of life. The current results in combination with three additional preparatory studies (expert survey, focus groups, clinical study) will provide the scientific basis for defining the ICF Core Sets for ASD for multi-purpose use in basic and applied research and every day clinical practice of ASD.