Instrument development and evaluation for patient-related outcomes assessments.

Patient-related outcomes measures could provide important information for the current state of the art in medical care and even have an impact on macrodecisions in the health care system. Patient-related outcomes were initially defined as subjective health indicators that allow disability and illness to be assessed, based on patient, caregiver, or physician self-reports. As illness involves psychological and behavioral complex processes of care, a multidisciplinary approach in measuring patient-reported outcomes should be recommended, such as quality of life questionnaires. Patient-related outcomes measures should correspond to specific clinical situations and bring opportunities to improve quality of care. Objective measurements enable quantitative data to be collected and analyzed. Depending on the aim of the research, investigators can use existing methods or develop new tools. This publication presents a methodology for developing patient-related outcomes measures, based on a multistage procedure. The proper definition of specific study objectives and the methodology of instrument development are crucial for successfully transferring the study concept. The model of instrument development is the process of starting from the preliminary phase and includes questionnaire design and scaling, pilot testing (cognitive debriefing), revision of the preliminary version, evaluation of the new tool, and implementation. Validation of the new instrument includes reliability, reproducibility, internal consistency, and responsiveness. The process of designing the new tool should involve a panel of experts, including clinicians, psychologists (preliminary phase), and statisticians (scale development and scoring), and patients (cognitive debriefing). Implementation of a new tool should be followed by evaluation study - assessment of the tool's usefulness in clinical practice. An instrument must show not only the expected methodological properties and performance but also a positive contribution to care. The necessity of implementation of direct patient-reporting methods has been highlighted by both the Food and Drug Administration and the European Medicines Agency.