title: Bidirectional (negative/positive) interference of oleandrin and oleander extract on a relatively new Loci digoxin assay using Vista 1500 analyzer.
abstract: BACKGROUND
  Oleander interferes with serum digoxin measurements using various immunoassays. The potential interference of oleander and its active ingredient, oleandrin, with a relatively new homogenous sequential chemiluminescent digoxin assay based on luminescent oxygen channeling technology (LOCI digoxin assay, Siemens Diagnostics) has not been previously reported.
  
  
  METHODS
  Aliquots of a digoxin-free serum pool were supplemented with increasing concentrations of oleandrin, or with oleander extract, followed by measuring the apparent digoxin concentrations using the LOCI digoxin assay using Vista 1500 analyzer. Mice were fed oleandrin or oleander extract, and their blood digoxin levels at 1 and 2 h were measured with the LOCI digoxin assay. In addition, two digoxin serum pools were prepared by combining sera of patients receiving digoxin; aliquots of both pools were supplemented with oleandrin or oleander extract and digoxin concentrations were again measured. Attempts to overcome this interference were made by measuring free digoxin concentration using a third digoxin pool.
  
  
  RESULTS
  Significant apparent digoxin concentrations were observed after supplementing aliquots of the drug-free serum pool with oleandrin or oleander extract. Mice fed with oleandrin or oleander extract also showed apparent digoxin levels 1 and 2 h after feeding. Digoxin values were also falsely lower or elevated (bidirectional interference) when aliquots of digoxin serum pools were further supplemented with oleandrin or oleander extract depending on concentration; this interference was not eliminated by free digoxin monitoring.
  
  
  CONCLUSIONS
  Oleandrin interferes with LOCI digoxin assay.
authors.affiliation: Department of Pathology and Laboratory Medicine, The University of Texas Medical School at Houston, Texas.
authors.forename: Amitava
authors.initials: A
authors.lastname: Dasgupta
authors.forename: Kerry J
authors.initials: KJ
authors.lastname: Welsh
authors.forename: Shen-An
authors.initials: SA
authors.lastname: Hwang
authors.forename: Myrtle
authors.initials: M
authors.lastname: Johnson
authors.forename: Jeffrey K
authors.initials: JK
authors.lastname: Actor
mesh_terms: D000818:Animals; D002298:Cardenolides / Q000097:blood*; D004077:Digoxin / Q000097:blood*; D006801:Humans; D008163:Luminescent Measurements / Q000295:instrumentation* / Q000379:methods*; D051379:Mice; D030007:Nerium / Q000737:chemistry*; D010936:Plant Extracts / Q000097:blood*
chemical_list: D002298:Cardenolides; D010936:Plant Extracts; D004077:Digoxin; C021065:oleandrin
keywords: LOCI digoxin assay; digoxin; interference; oleander