Stability of electrolyte determinations on the siemens advia 1800 analyzer

Background: It is sometimes necessary for the laboratory to re-test samples for critical serum electrolyte levels. It is important to assure reproducibility of results when testing is performed on stored, refrigerated samples. We have tested the reproducibility of results for the critical electrolytes, Na, K, Cl and Ca, from ten randomly selected patients'sera over our maximum storage period of nine (9) days on the Siemens Advia 1800 analyzer. The ranges for each electrolyte were 131-150 meq/L (Na), 3.4-5.2 meq/L (K), 101-123 meq/L (Cl) and 7.3-9.9 mg/dL (Ca). Methods: We used ion-selective electrodes for Na, K and Cl and the ortho-cresolphthalein dye method for Ca. Results: We find that the reproducibility of determinations for all of these electrolytes was excellent, i.e. the coefficients of variation for each electrolyte determination for each patient were low. Conclusion: The methods of measurement for these electrolytes on the Advia 1800 are reliable and reproducible.