Stability of Electrolytes in Whole Blood at Room Temperature Prior to Centrifugation: implications for Clinical Analysis

Background/Objectives The pre-analytical stability of electrolytes in capped whole blood at room temperature remains uncertain due to limited studies and inconsistent findings. This study investigates electrolyte stability during delayed centrifugation, in accordance with recent EFLM recommendations. Materials and methods The stability of electrolyte concentrations (sodium, potassium, chloride, and bicarbonate) was assessed in capped whole blood samples from 40 participants stored at room temperature at three time intervals (0, 2, and 4 hours) prior to centrifugation. Differences in electrolyte concentrations were expressed as percent deviation (%PD) from baseline (T0). The %PD for each analyte was calculated and compared with the maximum permissible difference (MPD), derived from intra- and inter-individual biological variation. Results The calculated MPD values for sodium, potassium, chloride, and bicarbonate were 1.5%, 4.2%, 1.9%, 10.8%, respectively. The mean %PD at 2 hours for sodium, potassium, chloride, and bicarbonate was 0.2, 0.1, -0.4, and -0.3, respectively. At 4 hours, the mean %PD values were 0.3, 2.1, -0.7, and -0.4, respectively. All mean %PD values remained within the MPD limits at both 2 and 4 hours, with potassium showing a higher mean %PD at the 4-hour time point compared to 2 hours. Conclusions Sodium and potassium concentrations increase over time, while chloride and bicarbonate concentrations decrease. Electrolytes in capped whole blood stored at room temperature with delayed centrifugation remained stable for up to 4 hours. However, potassium appeared to be more susceptible to changes due to delayed processing. . Timely sample handling is therefore critical to ensuring accurate electrolyte measurements.