Three-phase development of the health capital questionnaire: a mixed methods operationalization study

Background Health capital is emerging as a widely used conceptual framework offering an integrative sociocultural, economic, and behavioral resource-based perspective on individual health practices related to disease management and illness prevention. However, the full realization of its potential as an explanatory and predictive framework is currently somewhat constrained by the lack of an instrument that renders health capital observable. Objective We aimed to operationalize the health capital conceptual framework through the development of a comprehensive questionnaire-based instrument for the assessment of the multiplicity of components of health capital and their interactions. Materials and methods Drawing on the theoretical foundations of health capital, secondary evidence from a systematic literature review ( n = 23 included articles), and primary evidence from expert focus groups ( n = 23 experts) and projective techniques ( n = 2,118 respondents), we conducted a three-phase development process. In this process, we distilled topics, identified dimensions of health capital, synthesized questionnaire items, and mapped them into the Health Capital Questionnaire (HCQ). Results We developed the HCQ, comprising a total of 56 questions distributed over six sections, with translations into five languages: English, Italian, Romanian, Slovak, and Spanish. The mixed methods study employed in the development provided a solid basis for developing the questionnaire items for operationalizing the conceptual framework of health capital, demonstrating the viability of our proposed three-phase development process, which emphasizes validation-by-design in the absence of a clear external post hoc validation path. Conclusion The Health Capital Questionnaire, in its current form, functions as a multi-purpose instrument capturing perceptions, behaviors, experiences, preferences, and attitudes. It allows for the assessment of sociocultural, economic, and behavioral aspects of disease management and illness prevention in a theoretically integrative, culturally adaptable, and contextually extensible manner.