Bland–Altman plot for biochemically-tested potassium vs POC tested potassium. Unit of measurement, mmol/L. Standard deviation, 0.18; mean difference, 0.32 (0.31; 0.33); upper limit of the concordance correlation, 0.67 (0.65; 0.69); lower limit of the concordance correlation, −0.03 (−0.05; −0.01). Percentage analysis: mean difference, 8.45% (8.16%; 8.74%); upper limit of the concordance correlation, 17.91% (17.41%; 18.41%); lower limit of the concordance correlation, −1.01% (−1.51%; −0.51%). 95% confidence intervals. Regression line included.