Assessment of Hyperkalemia's Illness and Treatment Burden in Chronic Kidney Disease and Heart Failure Patients: HK Registry Pilot Study

Inclusion criteria

• Outpatients aged ≥20 years
• Hyperkalemia patients defined as meeting either of the following criteria:

• Having a history of S-K ≥5.1 mmol/L ≥2 times within 6 months before enrolment
• Having a history of S-K ≥5.5 mmol/L once within 6 months before enrolment
• Currently treated by potassium binders for the treatment of hyperkalemia at enrolment
• Having been diagnosed as CKD (≥stage 3b) or HFrEF by investigators as defined below:

CKD is diagnosed based on the guidelines of CKD issued by the Japanese Society of Nephrology (JSN, 2018) as being either or both of condition 1 and 2 for ≥3 months

• Clear sign of kidney impairment based on urinalysis, imaging, blood test, or biopsy. Especially, existence of ≥0.15 g/gCr of proteinuria (≥30 mg/gCr of albuminuria) is important.
• GFR <45 mL/min/1.73m2 Within the routine clinical practice, GFR is estimated by serum creatinine, gender, and age using following the formulation.

eGFR creat (mL/min/1.73m2) = 194 x serum creatinine (mg/dL)-1.094 x age (years)-0.287 (for female patients, x 0.739)

≥Stage 3b CKD is diagnosed based on the following eGFR categories:

• Stage 3b: 30 mL/min/1.73m2 ≤ eGFR <45 mL/min/1.73m2
• Stage 4: 15 mL/min/1.73m2 ≤ eGFR <30 mL/min/1.73m2
• Stage 5: eGFR <15 mL/min/1.73m2

Patients with HFrEF is enrolled if patients meet following criteria within 6 months:

• EF ≤40%
• NYHA class II-IV

• Provision of signed, written, and detailed informed consent
• Signed written informed consent by themselves

Exclusion criteria

• Currently on any chronic RRT (including hemodialysis or peritoneal dialysis >30 days, or kidney transplant) within 6 months before enrolment
• Patients with acute kidney injury at enrolment •Patients who took blood transfusion or potassium supplements within 6 months before enrolment
• Active malignancy or life expectancy of less than 6 months.
• Patients who have GI disturbance/chronic diarrhoea/stoma, and investigators determine those affect significantly serum K level
• Patients who have autoimmune disorders, and investigators determine those affect significantly serum K level
• Patients whose lab data have suspicion for pseudohyperkalemia
• Patients who are pregnant, lactating, or planning to become pregnant
• Current participation in interventional studies and/or clinical trials
• Patients who, in the opinion of the investigators, would be unlikely to comply with self-assessments