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

BackgroundLupus 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.MethodsThis 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.ResultsOverall, 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.ConclusionsThe 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. Lupus nephritis (LN) is a kidney involvement in many patients with systemic lupus erythematosus (SLE). SLE patients with LN may have clinical symptoms that include tiredness and changes regarding urine, in addition to those related to SLE itself, like rashes, joint pain and swelling. The symptoms can be mild, moderate or severe and can affect quality of life. It is important to learn the effects of these symptoms directly from the patients; understanding patients' experiences will help their medical team monitor the disease and treatment more effectively. Questionnaires are often used to evaluate symptoms and the impact of these symptoms on patients' lives. Two questionnaires, Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) and Lupus Quality of Life (LupusQoL), were used to assess symptoms and the effect of LN on the patients' lives. First, patients were asked to describe their signs and symptoms and how these affect their lives. Then, patients were asked about their understanding of the individual questions. We found that all patients reported symptoms of tiredness and joint pain. Increased urinary frequency, swelling in non-joints, and frequent infections were reported more often by patients with LN than those with SLE alone. Patients said that their manifestations greatly affect their everyday lives. There was a good understanding of the questionnaires, and patients felt the questions were relevant to them. This is an important step to validate FACIT-Fatigue and LupusQoL. This study shows that the FACIT-Fatigue and the LupusQoL can be used when assessing people with LN.