Performance of a novel spectrophotometric lithium assay on a routine biochemistry analyser.

A new spectrophotometric lithium assay was assessed after adaption to a Hitachi 917. Results on this analyser were in close agreement with lithium measured on a flame photometer (95% confidence interval+/-0.06 mmol/L, n = 120). Assay precision was <2.5% over a range of lithium concentrations from 0.5-3.0 mmol/L. The assay was linear to 3 mmol/L and interference from haemolysis, icterus, lipaemia and other metal ions was minimal. The assay is a useful substitute or "back-up" for traditional lithium assays. Improved "on-board" calibration stability (currently 24 h) is required by improving the stability of uncapped reagent.