Predictors of Somatic Symptom Persistence in Patients With Chronic Kidney Disease (RU SOMACROSS)

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Seven out of ten patients with chronic kidney disease (CKD) experience burdensome persistent somatic symptoms (PSS) in early stages of renal dysfunction. Despite their prevalence and relevance for quality of life, disease progression, and mortality, PSS in CKD is largely under-researched and under-treated. The pathogenesis of PSS in early-stage CKD remains poorly understood. Thus, only an integrated investigation of biomedical, treatment-related and psychosocial factors will unravel aetiological mechanisms and identify modifiable predictors of PSS in early stages of CKD.It is our overall objective to improve our understanding of how PSS in CKD develop and persist over time. First, we will investigate biopsychosocial predictors and their interactions for PSS in CKD in a multivariate prognostic prediction model. Second, we aim to identify unfavourable symptom trajectories and unravel their relations with biopsychosocial predictors over time. Third, we will experimentally test mechanisms of symptom perception, and qualitatively explore mechanisms of symptom development focussing on patients newly diagnosed with CKD. A mixed methods cohort study with assessments at baseline, 6, and 12 months will explore multivariate predictors of PSS in 330 patients with CKD stages 2-4. The primary outcome will be CKD-specific somatic symptom burden. Secondary outcomes include CKD-specific quality of life, general somatic symptom burden, and functioning. Predictors based on the adapted biopsychosocial working model of RU SOMACROSS include relevant biomedical (including epigenetic mechanisms and the biomarker suPAR), treatment-related (e.g., side effects), and psychosocial variables (e.g., expectations). Longitudinal structural equation models, latent class growth and cross-lagged panel analyses will be used. In an embedded mixed methods approach, an experimental study will use an affective picture paradigm to test the effect of negative affect induction on symptom perception and examine moderators. The embedded qualitative study will use thematic analysis to explore intrapersonal mechanisms by which patients develop somatic symptoms after receiving a new diagnosis of CKD. Focussing on subjective symptom burden instead of objective disease markers will fundamentally broaden our knowledge on PSS in CKD. Based on the adapted biopsychosocial RU SOMACROSS model, we will identify the relative impact of relevant biopsychosocial risk factors, explore promising new variables such as epigenetic alterations, suPAR, and patients’ expectations, and investigate interactions in the development and maintenance of PSS in CKD. Our results will contribute to RU SOMACROSS’ main objective to identify risk factors and mechanisms of PSS across diseases and inform the development of mechanism-based tailored interventions in CKD in the second funding phase.