Abstract
INTRODUCTION: Fatigue is frequently experienced in systemic lupus erythematosus (SLE) and is a key outcome in clinical research trials. However, SLE fatigue is complex and poorly understood, and challenging to measure. We aimed to characterise fatigue from the patients' perspective and develop a conceptual model of fatigue based on qualitative interviews. METHODS: We conducted semi-structured qualitative interviews exploring fatigue in patients with SLE recruited from a social network (n = 29) and a phase 2 clinical study (n = 43). Transcripts were coded thematically, and codes were inductively categorised into a conceptual model. RESULTS: Fatigue was the most commonly reported symptom in the interviews and generated a wide range of codes. From these, our concept-driven approach revealed three overarching domains of the fatigue experienced in SLE: (i) physical manifestation of physical and bodily symptoms (including physical energy, stamina and impact on movement); (ii) mental and cognitive manifestation (including mental energy, motivation, and cognitive functioning symptoms); and (iii) susceptibility to fatigue or how easily 'fatigable' patients are, meaning how easily they become fatigued and how easily their fatigue is alleviated (including the rapid, disproportionate, and/or unpredictable onset of fatigue, non-restorative sleep, and need for more sleep/rest breaks). Within each of these, participants described the severity, variation and impact of fatigue on everyday life. Participants also described how the SLE fatigue experience differed from 'everyday tiredness'. CONCLUSIONS: The findings of this research indicate that comprehensive measurement of fatigue in SLE will require consideration and quantification of the three domains described in our conceptual model. Future research will explore whether this conceptual model can form the basis of a valid and reliable measurement of fatigue in SLE.