Dear Editor, Sodium ion is the predominant cation in extracellular fluid, and its accurate measurement is crucial for clinical diagnosis and patient management. The Vitros 5600 automatic biochemical immunoassay analyzer (Johnson 2 hours, 141.9 ± 1.52; 4 hours, 141.0 ± 1.40; 6 hours, 141.0 ± 1.45; and 8 hours, 140.8 ± 1.42 mmol/l. Significant differences were observed between the 1-/2-hour groups and all other time points (P 0.05), indicating that sodium concentrations stabilized after 4 hours of equilibration (Fig. 1). Figure 1.: Relationship between rewarming time and sodium ion concentration. Our findings demonstrate that sodium dry slides require at least 4 hours of room-temperature equilibration to achieve stable and reliable results. The higher sodium concentrations at 1 and 2 hours may be attributed to incomplete rewarming and potential moisture absorption. This study suggests that the manufacturer’s recommended 2-hour minimum equilibration time may be insufficient for sodium measurement. Clinical laboratories should ensure a minimum equilibration time of 4 hours to guarantee accurate sodium results. Ethical approval This study was a laboratory-based method validation using only anonymous residual clinical serum samples. No human subjects or identifiable patient data were involved. Ethical approval was not required. Consent Informed consent was not required, as all samples were residual anonymous laboratory specimens without any personal patient information included. Conflicts of interest disclosure The authors declare no conflicts of interest related to this study. Sources of funding This study received no external funding for this research and manuscript. Author contributions Bin Cheng designed the study, performed the experiments, analyzed the data, and drafted the manuscript. All authors reviewed and approved the final submission. Research registration unique identifying number (UIN) Not applicable. This was an in vitro laboratory study and did not require clinical research registration. Guarantor Bin Cheng is the guarantor of this study and takes full responsibility for the manuscript and all related data. Provenance and peer review Not applicable. Data availability statement Not applicable. Acknowledgements Not applicable.
Cheng et al. (Fri,) studied this question.