Patient reported outcome measures: a model-based classification system for research and clinical practice

PURPOSE: The umbrella term Patient Reported Outcomes (PRO) has been successfully proposed for instruments measuring perceived health outcomes, but its relationship to current conceptual models remains to be established. Our aim was to develop a classification system for PRO measures based on a valid conceptual model. METHODS: We reviewed models and classification schemes of health outcomes and integrated them in a common conceptual framework, based on the models by Wilson and Cleary and the International Classification of Functioning (ICF). We developed a cross-classification system based on the minimum common set of consistent concepts identified in previous classifications, and specified categories based on the WHO International Classifications (ICD-10, and ICF). We exemplified the use of the classification system with selected PRO instruments. RESULTS: We identified three guiding concepts: (1) construct (the measurement object); (2) population (based on age, gender, condition, and culture); and (3) measurement model (dimensionality, metric, and adaptability). The application of the system to selected PRO measures demonstrated the feasibility of its use, and showed that most of them actually assess more than one construct. CONCLUSION: This classification system of PRO measures, based on a valid integrated conceptual model, should allow the classification of most currently used instruments and may facilitate a more adequate selection and application of these instruments.