Kavain Interference with Amphetamine Immunoassay

We encountered unexpected false positive urine results in three patients for amphetamine-type substances by immunoassay, measured as part of community drug prevention programmes. Kavain was identified in all three urine samples by gas chromatography mass spectrometry (GC-MS). No other potential cross-reactants were found.Kavain is a kava-lactone present in kava, a ceremonial and recreational drink derived from roots and stem of the plant Piper Methysticum. It is consumed regularly by many indigenous Pacific and Australian Aboriginal communities.

Urine immunoassay was performed on a Beckman Coulter AU480 Analyser using CEDIA amphetamine-type substances reagent and DRI ethanol reagent. Three different kava powders were purchased from local kava clubs and dissolved in ethanol, then evaporated and reconstituted in blank urine and analysed by immunoassay, GC-MS for amphetamine-type substances. Additionally authentic kavain standard was also tested for cross reactivity by immunoassay and analysed by GC-MS to compare the mass fragmentation pattern and retention time with the kava powder and patient specimens.

The patient urine samples tested positive by CEDIA immunoassay for amphetamines. However, when analysed by GCMS they were negative for amphetamine-type but contained kavain.The kava powders and kavain standard all cross reacted with the amphetamine immunoassay to give falsely detected results. GCMS did not identify any amphetamine-type compounds in any of the Kava powders nor in the kavain standard.

To our knowledge, this is the first report of false positive amphetamine measurements due to kavain, a component of the kava drink, widely consumed in Oceania and Australasia.