RESUMO
BACKGROUND: To prepare for a longitudinal study of the effects of potassium-lowering treatment on quality of life (QOL), we quantified the validity of a new disease-specific instrument for measuring QOL, using data from patients who had hyperkalemia (HK) due to chronic kidney disease (CKD) or chronic heart failure, and were also being treated with potassium binders (PBs). METHODS: In this cross-sectional study, the participants were 98 patients at five outpatient clinics in Japan. The outcome measures were the Medical Outcomes Study 36-item short-form (SF-36), a widely used generic measure of QOL, and the Quality of Life Disease-specific Impact Scale (QDIS-7), a recently-developed disease-specific measure of QOL. Internal-consistency reliability was quantified, and factor analysis was done to confirm hypothesized QOL dimensions. Validation tests used two external criteria: CKD stage, and PB formulation. PB formulation was used because different formulations are associated with different degrees of patients' burden. Using a previously-described method, we computed the relative validity (RV) of the two measures. RESULTS: Two factor scoring of the SF-36 and one factor scoring of the QDIS-7, as standardized from previous studies, were confirmed. The RVs showed that the QDIS-7 was much more valid than the SF-36, for discriminating between groups defined clinically (by CKD stage), and also between groups defined by PB formulation. Reliability was satisfactory: 0.73-0.95 for the SF-36 and 0.86 for the QDIS-7. CONCLUSIONS: The QDIS-7 with CKD or PB attributions was more valid than the SF-36 for measuring the effects of CKD and of PB formulation on QOL.
RESUMO
INTRODUCTION: Hyperkalaemia (HK) is a frequent complication in patients with chronic kidney disease (CKD) and/or chronic heart failure (CHF). HK must be managed, both to protect patients from its direct clinical adverse outcomes and to enable treatment with disease-modifying therapies including renin-angiotensin-aldosterone system inhibitors. However, the experiences of patients undergoing treatment of HK are not clearly understood. Optimising treatment decisions and improving long-term patient management requires a better understanding of patients' quality of life (QOL). Thus, the aims of this research are: (1) to describe treatment patterns and the impact of treatment on a patient's QOL, (2) to study the relationships between treatment patterns and the impact of treatment on a patient's QOL and (3) to study the relationships between the control of serum potassium (S-K) and the impact of treatment on a patient's QOL, in patients with HK. METHODS AND ANALYSIS: This is a prospective cohort study with 6 months of follow-up in 30-40 outpatient nephrology and cardiology clinics in Japan. The participants will be 350 patients with CKD or CHF who received their first potassium binders (PB) prescription to treat HK within the previous 6 months. Medical records will be used to obtain information on S-K, on treatment of HK with PBs and with diet, and on the patients' characteristics. To assess the impact of treatment on a patient's QOL, questionnaires will be used to obtain generic health-related QOL, CKD-specific and CHF-specific QOL, and PB-specific QOL. Multivariable regression models will be used to quantify how treatment patterns and S-K control are related to the impact of treatment on a patient's QOL. ETHICS AND DISSEMINATION: Institutional review boards at all participating facilities review the study protocol. Patient consent will be obtained. The results will be published in international journals. TRIAL REGISTRATION NUMBER: NCT05297409.