Reference Intervals of Serum Sodium, Potassium, and Chlorine in Chinese Han Population and Comparison of Two ISE Methods.

Background: Currently there are no reference intervals (RIs) of sodium (Na), potassium (K), and chlorine (Cl) on Chinese population. Two kinds of ion-selective electrode (ISE) methods were commonly used to determine K, Na, and Cl levels in China, the difference between these two methods needs to be evaluated.

Methods: A total of 4,524 healthy participants (1,916 males and 2,608 females) between 20-79 years old from six cities in China were selected by strict criteria. Serum K, Na, and CL were tested on Roche Modular analyzers in six assigned laboratories. According to EP-9A2, using Roche Modular analyzer (indirect ISE) as comparative method, Olympus AU 5400 analyzer (indirect ISE) and Johnson&Johnson Fusion 5.1 analyzer (direct ISE) were evaluated.

Results: In Chinese population, the RIs for K, Na, and CL are 3.6-5.2, 136-146, and 99-110 mmol/l, respectively. Compared to the Roche indirect ISE method, Johnson direct ISE method showed a positive bias; and Olympus indirect ISE method just showed a very slight bias.

Conclusion: The RIs of K, Na, and Cl of Han Chinese healthy adult population were found to be smaller than those provided by the manufacturer. By a criteria of biological variations for CV, the differences of Na and K between Roche analyzer and Johnson analyzer were not acceptable for clinical application, while the differences of Na, K, and Cl between Roche and Olympus analyzers were acceptable for clinical application.