title: Do all screening immunoassay positive buprenorphine samples need to be confirmed?
abstract: Background Interference from opiates in the Microgenics CEDIA® Buprenorphine assay is known to produce false-positive buprenorphine screening immunoassay results necessitating confirmatory buprenorphine testing by chromatography/mass spectrometry methods. Method We reviewed data on falsely positive buprenorphine immunoassay screen (cut-off ≥ 5  µg/L) but negative for buprenorphine by gas chromatography mass spectrometry (cut-off ≥ 5  µg/L) and had a positive opiate immunoassay result (cut-off ≥ 300  µg/L). The results were collected over three months, and the data were evaluated to determine whether there is an opiate immunoassay screen concentration below which a false-positive buprenorphine result will not occur. Results We found that cross-reactivity in the CEDIA® buprenorphine immunoassay by opiates at concentrations <2000  µg/L will not cause a false-positive buprenorphine result. After changing our practice to not proceed with confirmatory buprenorphine gas chromatography mass spectrometry assay when the opiate screening concentration is below an even more conservative cut-off of <1500  µg/L, we estimate a potential cost-saving of AU$ 17,810 per year without compromising clinical care. Conclusion Samples with CEDIA® opiate immunoassay result <2000  µg/L and a positive CEDIA® buprenorphine immunoassay screen do not require confirmatory testing for buprenorphine.
authors.affiliation: Chemical Pathology Directorate, South Australia Pathology, Adelaide, Australia.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Saleem
authors.affiliation: Chemical Pathology Directorate, South Australia Pathology, Adelaide, Australia.
authors.forename: Helen
authors.initials: H
authors.lastname: Martin
authors.affiliation: Chemical Pathology Directorate, South Australia Pathology, Adelaide, Australia.
authors.forename: Anne
authors.initials: A
authors.lastname: Tolya
authors.affiliation: Chemical Pathology Directorate, South Australia Pathology, Adelaide, Australia.
authors.forename: Penny
authors.initials: P
authors.lastname: Coates
mesh_terms: D002047:Buprenorphine / Q000032:analysis*; D002138:Calibration; D005189:False Positive Reactions; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007118:Immunoassay / Q000379:methods* / Q000592:standards; D015203:Reproducibility of Results; D015813:Substance Abuse Detection
chemical_list: D002047:Buprenorphine
keywords: Buprenorphine; confirmatory testing; cross-reactivity; opiates; urine drug screen