Falsely elevated lithium levels in plasma samples obtained in lithium containing tubes.
METHODS
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.


CONCLUSIONS
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).
Lee
D C
DC
Medical College of Pennsylvania, Philadelphia.
Klachko
M N
MN
D000328:Adult; D062787:Drug Overdose; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007223:Infant; D008094:Lithium / Q000097:blood*; D016651:Lithium Carbonate / Q000506:poisoning*; D008297:Male; D009661:Nortriptyline / Q000506:poisoning*; D013048:Specimen Handling / Q000379:methods*
D016651:Lithium Carbonate; D008094:Lithium; D009661:Nortriptyline