Cross-reactivity of the CEDIA buprenorphine assay with opiates: an Austrian phenomenon?

When testing the Microgenics CEDIA assay for immunological buprenorphine analysis, cross-reactivity between the buprenorphine reagents and opiates was observed at concentrations higher than 120 mg/l morphine, 320 mg/l methadone, 30 mg/l codeine, 60 mg/l dihydrocodeine and 520 mg/l morphine-3-glucuronide. The cross-reactivity with morphine has the greatest impact on routine screening as opiate maintenance therapy in Austria is also performed with slow-release oral morphine. The use of a second cutoff value of 30 μg/l for urine samples that are (immunologically) positive for opiates is therefore suggested, compared to the cutoff value of 5 μg/l proposed by the manufacturer.