Agreement of serum potassium measured by blood gas and biochemistry analyzer in patients with moderate to severe hyperkalemia

PurposeSeveral studies investigated the agreement between central laboratory biochemistry analyzers and blood gas analyzers for potassium measurements. However, data are scarce when the potassium level is moderate to severely high. We aimed to evaluate the agreement between central laboratory biochemistry analyzers and blood gas analyzer in terms of serum potassium level measurement because differences in potassium at this level translate into very different clinical actions.Basic proceduresThis was a retrospective medical record review study in which patients who presented to the emergency department and had serum potassium levels ≥ 6 mmol/L were included. Patients who did not have simultaneous potassium measurement by blood gas analyzer were excluded. We included all patients meeting potassium criteria irrespective of their underlying disease or comorbidities. We evaluated agreement between the measurement methods with Pearson correlation, Bland-Altman plot, and Sign test.Main findingsA total of 118 blood sample pairs were included. The mean serum potassium level measured by biochemistry analyzer was 6.78 ± 0.79 mmol/L, whereas it was 6.16 ± 0.86 mmol/L by blood gas analyzer (P < .001, Sign test). There was a strong correlation (P < .001, r = 0.864) between the 2 methods, but agreement was relatively poor. Blood gas analyzer tended to measure potassium significantly lower than measured by biochemistry analyzer. The mean difference between the methods was 0.62 ± 0.43 mmol/L.Principal conclusionsIn patients with moderate to severe hyperkalemia, blood gas analyzer and biochemistry analyzer gives significantly different serum potassium results which may be clinically important.