Figure 1. Development and Validation Data Sets Generation and Electrocardiogram (ECG) Labeling of Hyperkalemia.

To convert potassium to millimoles per liter, multiply by 1.

^aEstimated glomerular filtration rate calculated from the Chronic Kidney Disease Epidemiology Collaboration equation, using the mean serum creatinine values within 24 hours prior to time of ECG recording.

^bGiven error in serum potassium, and to avoid potentially irrelevant misclassification rates around hyperkalemia threshold, ECGs with serum potassium greater than 5.3 mEq/L or less than 5.7 mEq/L were excluded.

^cRandom ECG selected for Minnesota dataset. Most recent ECG selected for Arizona and Florida datasets.