title: Evaluation of human serum albumin cobalt binding assay for the assessment of myocardial ischemia and myocardial infarction.
abstract: BACKGROUND
  Clinical diagnoses were correlated with results of a Co(II)-albumin binding assay in 167 patients treated at an emergency department of a health maintenance organization.
  
  
  METHODS
  Patients were evaluated as being nonischemic or potentially ischemic through standard coronary disease indicators [creatine kinase (CK), CK-MB, cardiac troponin I, and electrocardiographic findings] and were tested by a Co(II)-albumin binding assay. Samples were tested anonymously, and the study was double-blinded. The sensitivity and specificity of this assay for the detection of ischemia were evaluated by ROC curve analysis. Known Co(II) binding sites on albumin were analyzed by N-terminal amino acid sequencing.
  
  
  RESULTS
  The mean absorbance units (ABSU) +/- 2 SD for non-myocardial ischemic and myocardial ischemic individuals measured at 470 nm were 0.43 +/- 0.10 and 0.63 +/- 0.25, respectively (P <0.0001). The area under the ROC curve was 0.95 [95% confidence interval (CI), 0.92-0.99], and at a cutoff value of 0.50 ABSU, sensitivity and specificity were 88% (78-94%) and 94% (86-98%), respectively, suggesting a high distinction between the two groups. When we compared non-acute myocardial infarction (AMI) and AMI ischemic individuals, the area under the ROC curve was 0.66 (95% CI, 0.53-0.79) and was considered a poor discriminator between these two groups. N-Terminal amino acid sequencing data for purified albumin showed normal amino acid residues for six of seven high-ABSU (> or =0.70) individuals and one nonischemic individual tested. However, only one individual with a high ABSU (0.80) had two missing amino acid residues (DA) from the N-terminal region. Clinical diagnosis for this patient did not reveal an ischemic event.
  
  
  CONCLUSIONS
  The Co(II)-albumin binding test may serve as a useful diagnostic tool in emergency facilities for the assessment of myocardial ischemia. High and low ABSU were associated with myocardial ischemic individuals and non-myocardial ischemic individuals, respectively. However, the Co(II)-albumin binding was a poor discriminator between ischemic individuals with and without MI.
authors.affiliation: Department of Biochemistry and Biophysics, John A. Burns School of Medicine, University of Hawaii, Honolulu 96822, USA. bhagavan@hawaii.edu
authors.forename: Nadhipuram V
authors.initials: NV
authors.lastname: Bhagavan
authors.forename: Ernest M
authors.initials: EM
authors.lastname: Lai
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Rios
authors.forename: Jinsheng
authors.initials: J
authors.lastname: Yang
authors.forename: Anna M
authors.initials: AM
authors.lastname: Ortega-Lopez
authors.forename: Hiroko
authors.initials: H
authors.lastname: Shinoda
authors.forename: Stacey A A
authors.initials: SA
authors.lastname: Honda
authors.forename: Carlos N
authors.initials: CN
authors.lastname: Rios
authors.forename: Cheryl E
authors.initials: CE
authors.lastname: Sugiyama
authors.forename: Chung-Eun
authors.initials: CE
authors.lastname: Ha
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001665:Binding Sites; D015415:Biomarkers / Q000097:blood; D003035:Cobalt / Q000737:chemistry*; D005260:Female; D006801:Humans; D007202:Indicators and Reagents; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis; D017202:Myocardial Ischemia / Q000175:diagnosis*; D011485:Protein Binding; D012372:ROC Curve; D012709:Serum Albumin / Q000737:chemistry*
chemical_list: D015415:Biomarkers; D007202:Indicators and Reagents; D012709:Serum Albumin; D003035:Cobalt