Research Paradigm of the International Classification of Functioning, Disability and Health (ICF) With Item Response Theory: Clarification, Classification, and Challenge

Background: The International Classification of Functioning, Disability and Health (ICF) is the worldwide terminology system for measuring health and disability at both individual and population levels. However, the underlying challenges remain in achieving widespread adoption and implementation of ICF within healthcare contexts, including the unequal interval scale of the ICF Likert-type qualifier system ranging from 0 to 4, a lack of consensus on conceptualization and grading criteria of ICF items, and an excessive number of ICF items associated with each disease. The utilization of item response theory (IRT) for ICF studies demonstrated potential benefits in addressing these issues. Here, a review attempted to provide clarification of two predominant needs (sufficiency and efficiency) and two dimensions of scoring principles (stratification and assignment principles) in the ICF.

Methods: A literature search was conducted on the PubMed database, and 44 relative articles were selected. On this basis, this review was undertaken to track the research progress of the ICF based on the parameter IRT method, typically the Rasch model.

Results: This review outlined the classification of Item response model (IRM) for ICF studies and summarized existing IRT-based ICF research paradigms. Moreover, this review identified blind spots regarding assignment principles and the difficulty parameter in current ICF-based IRT studies. The Mokken scale analysis (MSA), as a non-parametric IRT method, was introduced as a data shaping tool for parametric IRM. The pipeline of the ICF-based MSA-Rasch modeling might advance the understanding of ICF clinical application and shed light on a new paradigm of questionnaire design.

Conclusion: The advent of ICF-oriented IRM algorithms may advance the comprehension of ICF clinical application and pave the way for a new paradigm for IRT-derived ICF questionnaires, namely the parsimonious ICF core set. Additionally, the Wright map holds promise in facilitating insight into rehabilitation trajectories and personalizing rehabilitation goals.