A study to examine the accuracy of potassium measurements in clinical laboratories across Canada

Diabetic ketoacidosis: difference between potassium determined by blood gas analysis versus plasma measurement

OBJECTIVE: To evaluate the accuracy of potassium concentrations measured by blood gas analysis (PBG) compared with laboratory serum potassium (LSP), in the initial care of patients with diabetic ketoacidosis (DKA). SUBJECTS AND METHODS: Fifty three patients with diabetes mellitus were evaluated in a retrospective analysis. PBG was carried out using the Radiometer ABL 700 (Radiometer Copenhagen®), and results were compared with LSP ADVIA 1650 Chemistry system (Siemens®), the gold standard method. Both methods are based on potentiometry. RESULTS: Mean PBG was 3.66 mmol/L and mean LSP was 4.79 mmol/L. Mean difference between PBG and LSP was -1.13 mmol/L (p < 0.0005, 95% CI, -1.39 to -0,86). Lin concordance correlation coefficient was rc = 0.28 (95% CIb, 0.10 to 0.45), demonstrating low concordance between the methods. CONCLUSION: Although PBG measurement is faster and easier, it should not be used as a surrogate for LSP in the clinical treatment of DKA.