title: Evaluation of the albumin cobalt binding (ACB) assay for measurement of ischaemia-modified albumin (IMA) on the Beckman Coulter LX-20.
abstract: BACKGROUND
  In the presence of ischaemia, albumin undergoes changes resulting in the formation of ischaemia-modified albumin (IMA). Increased serum concentrations of IMA have been found in patients with myocardial ischaemia. The purpose of this study was threefold: to evaluate the albumin cobalt binding (ACB) assay for measurement of IMA on the Beckman Coulter LX-20; to establish a reference range for IMA; and to investigate the relationship between IMA and total albumin concentrations.
  
  
  METHODS
  The ACB assay was evaluated under the following headings: imprecision, accuracy and reliability. A reference range was established on a population of 81 healthy subjects.
  
  
  RESULTS
  The within-batch coefficient of variation (CV) at IMA concentrations of 88, 99 and 120 KU/L were 1.4, 2.0 and 2.5%, respectively. The between-batch CVs at 74, 84 and 123 KU/L were 3.4, 3.3 and 3.0%, respectively. Comparison with the Cobas Mira Plus showed a mean negative bias of 7 KU/L. The 97.5th percentile established on our reference population was 110 KU/L. A significant inverse relationship was found between total serum albumin and IMA concentrations (r = -0.66, P < 0.0001). Correcting the IMA concentrations for total albumin in our reference population, using a formula devised in this study, yielded a range similar to that of uncorrected IMA.
  
  
  CONCLUSIONS
  The ACB assay was found to have acceptable precision and performed very satisfactorily on the Beckman Coulter LX-20. A correction to measured IMA concentrations, to take into account total albumin concentrations, may need to be applied for the proper interpretation of IMA results.
authors.affiliation: Clinical Biochemistry Department, St Vincent's University Hospital, Elm Park, Dublin 4, Ireland. o.maguire@st-vincents.ie
authors.forename: Orla C
authors.initials: OC
authors.lastname: Maguire
authors.forename: Jean
authors.initials: J
authors.lastname: O'Sullivan
authors.forename: John
authors.initials: J
authors.lastname: Ryan
authors.forename: Sean K
authors.initials: SK
authors.lastname: Cunningham
mesh_terms: D001322:Autoanalysis / Q000379:methods; D003035:Cobalt / Q000378:metabolism*; D006801:Humans; D017202:Myocardial Ischemia / Q000175:diagnosis; D011933:Reagent Kits, Diagnostic / Q000592:standards*; D012709:Serum Albumin / Q000378:metabolism*
chemical_list: D011933:Reagent Kits, Diagnostic; D012709:Serum Albumin; D003035:Cobalt