The WHO construct of health-related functioning (HrF) and its implications for health policy

BACKGROUND: The International Classification of Functioning (ICF) has acquired a central role in the WHO Family of International Classifications and it has been extensively adopted as the reference framework for health-related functioning (HrF). This review aims to provide a description of the ICF/HrF to contextualise ICF/HrF in relation to other approaches to health functioning and to describe its application in policy and legislation with a special focus on Spain. METHODS: Narrative review based on the scientific literature and prior expert knowledge. RESULTS: ICF is both a coding system and a conceptual framework of HrF, which is framed as a unidimensional, bipolar and asymmetric construct with a negative pole (disability) and a positive pole (good functioning) with higher complexity. Other models of HrF include health promotion, quality of life and activities of daily living (ADL). The curtailed taxonomy of ICF and its unclear distinction from other approaches have had significant implications for research, policy and legislation, as illustrated by the case of the legislation and services for functional dependency in Spain and other examples. CONCLUSIONS: The ICF model of functioning is more comprehensive and usable than previous alternatives, but a full taxonomy of the HrF construct is needed to avoid further confusions in this field. This should also comprise harmonisation with other classifications of the WHO Family of International Classifications and other models of health functioning.