Falsely Elevated Lithium Levels in Plasma Samples Obtained in Lithium Containing Tubes

Abstract

We present a case of lithium poisoning in a 15-month-old child. Delayed elevation of the plasma lithium concentration at 13 hours after admission to a hospital was noted. This appeared to be factitiously related to the collection of samples in a speckled green top tube which contains lithium heparin as an anticoagulant. This type of false elevation has not been reported in the medical literature. A follow-up study in five healthy volunteers showed that the lithium concentrations of plasma samples obtained in speckled green top tubes are increased by approximately 1.5 mEq/L (1.5 mmol/L).