AK+ Guard™ Pilot Study in Chronic Kidney Disease: Outpatient Diagnostic Accuracy and Remote Monitoring

The goal of this observational pilot study is to evaluate the investigational AK+ Guard™ software as a medical device (SaMD) for detection of moderate to severe hyperkalemia (serum potassium (K+) ≥ 6.5 mmol/L) in adults with chronic kidney disease (CKD). Study objectives are: * Arm 2A (Outpatient Diagnostic Accuracy): To generate a preliminary, real-world signal of the diagnostic performance of AK+ Guard™ when used in an ambulatory CKD cohort for identifying clinically significant hyperkalemia episodes (serum K+ ≥ 6.5 mmol/L) at the time of an outpatient laboratory draw. * Arm 2B (Remote Patient Monitoring): To assess participant compliance, usability, and end-to-end system reliability of AK+ Guard™ when deployed for daily remote monitoring of CKD patients outside the clinical environment for up to four weeks.

Inclusion Criteria: (Arm 2A - Outpatient Diagnostic Accuracy) * Age 22 years or older * CKD stages III-IV managed at Central Jersey Kidney Care outpatient clinic * Scheduled outpatient serum potassium laboratory test * On RAASi therapy or documented hyperkalemia (K+ ≥ 5.5 mmol/L) within the past 12 months * Able to provide written informed consent (Arm 2B - Remote Patient Monitoring) * Completion of Arm 2A visit * Owns an iPhone compatible with the study application Exclusion Criteria (Both arms): * Age 21 years or younger * Pacemaker or implantable cardioverter defibrillator * Pre existing Left Bundle Branch Block (LBBB), Right Bundle Branch Block (RBBB), Intraventricular Conduction Delay (IVCD), or clinically significant hypocalcemia * Potassium lowering treatment administered before Lead I ECG acquisition * Trauma, acute events, or active interventions altering potassium homeostasis * Physical limitation precluding ECG acquisition