Strengths and limitations of the draft classification of public health interventions in the World Health Organization’s International Classification of Health Interventions: A developmental appraisal

Statistical classifications provide a basis for collecting and analysing data, for building knowledge and communicating information. A classification of public health interventions is being developed as part of the World Health Organization’s International Classification of Health Interventions (ICHI). This is a pioneering development, as there have been no previous efforts to produce a standard classification of public health interventions. A comprehensive developmental appraisal of the draft classification of public health interventions was undertaken to gain an understanding of its strengths and limitations, and to identify what should be done to improve its utility. The classification was used to code three data sets of public health interventions, to identify problems encountered and to assess inter-coder reliability. Views of potential users were elicited through key-informant interviews. An analytical structure was developed, comprising a set of criteria concerning the desired features of a statistical classification and a model representing the main elements that make up a statistical classification. ICHI was found to have some utility for representing data on public health interventions. Limitations identified included coverage gaps, overlap between categories, lack of clarity concerning how the classification axes are operationalised for public health interventions, and difficulty splitting complex interventions into their constituent components for coding. This study makes a significant and timely contribution to the development of the draft classification, by providing specific proposals for improvements to ICHI, explicating some fundamental conceptual issues that should be addressed, and indicating a path forward for the further development and use of ICHI in the field of public health. The analytical structure developed through the conduct of this research represents a novel methodological contribution to the field of classification development.