Evaluation of human serum albumin cobalt binding assay for the assessment of myocardial ischemia and myocardial infarction.
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.
Bhagavan
Nadhipuram V
NV
Department of Biochemistry and Biophysics, John A. Burns School of Medicine, University of Hawaii, Honolulu 96822, USA. bhagavan@hawaii.edu
Lai
Ernest M
EM
Rios
Patricia A
PA
Yang
Jinsheng
J
Ortega-Lopez
Anna M
AM
Shinoda
Hiroko
H
Honda
Stacey A A
SA
Rios
Carlos N
CN
Sugiyama
Cheryl E
CE
Ha
Chung-Eun
CE
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*
D015415:Biomarkers; D007202:Indicators and Reagents; D012709:Serum Albumin; D003035:Cobalt