Fatigue in rheumatoid arthritis: from patient experience to measurement

Many patients with rheumatoid arthritis (RA) complain about fatigue. In-depths interviews with patients showed that fatigue is experienced as an annoying symptom that can have far-reaching consequences for daily life. However, not each patient has the same experience of fatigue: emotions, consequences and coping with fatigue differed by age and gender. In a study using a card-sort method (Q-sort), four groups of patients sharing a comparable perspective on the experience of fatigue were found: “Little impact of fatigue”, “Good coping and bad sleep”, “Search for balance”, and “High distress”. The causes for fatigue in RA are not yet fully understood. A systematic review of studies that examined potential causes and consequences of fatigue in RA showed that pain, depression and physical disability were frequently associated with fatigue. However, more research is needed to draw conclusions about casual relationships. It is also unclear whether (biologic) medication does have effect on fatigue in RA. To evaluate potential treatment effects it is necessary to measure fatigue adequately. This thesis provides important insights into meaning and measurement of fatigue in RA. Existing measurement instruments for fatigue were not developed from the patients’ perspective and /or are traditional questionnaires. In contrast, in a computerized adaptive test (CAT) questions are selected automatically based on the previous answer of a patient. So it is no longer necessary that patients fill in questions that are not applicable to their level of fatigue and can be measured precisely with few items. This thesis describes the development of an item pool for the measurement of fatigue in RA and how the perspective of patients and health professionals was included by using a Delphi approach. The product is a preliminary calibrated item bank that will be used for the construction of a computerized adaptive test (CAT) for fatigue in RA in a consecutive project.