Patient-reported outcome measures for lupus nephritis: content validity of LupusQoL and FACIT-Fatigue

Lupus nephritis (LN), a severe organ manifestation of systemic lupus erythematosus (SLE), significantly impacts health-related quality of life (HRQoL). Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) and Lupus Quality of Life (LupusQoL) have been validated to measure HRQoL in SLE, but not specifically in LN. Patient-reported symptoms of LN are not well-reported. We assessed the content validity and relevance of these measures in evaluating patients with LN and their LN-related experiences.

This qualitative, interview-based study enrolled patients with LN from three US sites from a larger, retrospective survey study. The interview comprised an open-ended concept elicitation part and a more structured cognitive part. Concept elicitation was used to identify relevant themes describing the patients' experiences. Patients were asked to describe their LN-related symptoms, the severity and impact of those symptoms and their satisfaction with treatment. A cognitive interview approach evaluated the appropriate understanding of the items, instructions, and response options and asked patients about their understanding of the FACIT-Fatigue or LupusQoL measures, their relevance to the condition, and any aspects of confusion or need for better clarity of the questionnaires. All interviews were recorded and transcribed. The concept elicitation data were coded, while the cognitive interview data were tabulated to present the participants' responses next to the interview questions to support the evaluation of their understanding of the questionnaire items.

Overall, 10 patients participated in FACIT-Fatigue and another 10 in LupusQoL interviews; 18 patients were female, 10 were Black (self-reported) and 17 were receiving maintenance treatment for LN with stable disease activity. When patients recalled their symptoms, 670 expressions of varying symptoms were reported. All patients described pain, discomfort, and energy-related symptoms. Urinary frequency and non-joint swelling were most frequently attributed to LN rather than SLE. Patients felt the questions asked in the FACIT-Fatigue and LupusQoL surveys were relevant to their LN experience.

The symptoms reported by patients with LN were consistent with symptoms reported by the overall SLE population. However, patients indicated that some symptoms of LN were more profound than symptoms of SLE alone, affecting a broad range of areas of daily life activity and resulting in a higher burden on their HRQoL. FACIT-Fatigue and LupusQoL demonstrated content relevance as meaningful tools for patients with LN. However, further quantitative data collection is needed to ensure that these patient-reported outcome tools demonstrate good measurement properties in an LN population.