Influences of Sample Collection and Pre-Treatment on Lithium Assay with Ion Selective Electrode Method

Abstract

The aim of this study was to explore the various pre-analytical influence factors on a sample's lithium measurement with the ion selection electrodes method. Eighty nine in-hospital patients who have taken lithium carbonic acid treatment were recruited. The blood samples were collected under different conditions to compare the lithium concentration difference which was determined with an Eashlyte® electrolyte analyzer. Lithium in samples collected at different time periods varied at the range from minimum 0.47 mmol/L to maximum 1.20 mmol/L. Lithium in samples with hemolysis, hyperlipemia and separation gel treatment were all higher than that in common sera. Lithium in whole blood was significantly higher than that in plasma and it diminished with a decrease of red blood cell number (P < 0.05). Lithium in coagulant-treated samples and plasma had no significant difference with that in common sera (P > 0.05). In samples treated with different conditions, without clot separation, in all samples lithium increased (P <0.05-0.001) after being stored at room temperature. After serum separation, lithium in sera after being stored for 24 h was no different at room temperature than at 4 ºC (P > 0.05). Lithium concentration assayed with the ion selection electrodes method was greatly impacted with the use of different sampling and pre-treatment methods.