Significance Of Serum Ischemia-Modified Albumin Levels On The Diagnosis Of Acute Coronary Syndromes And A Preliminary Analysis Of Its Protein Structure

Objective To establish albumin cobalt-binding(ACB) test for ischemia- modified albumin (IMA) detection; to evaluate serum IMA levels in healthy persons of different genders and ages and determine appropriate cut-off value; to evaluate its early diagnostic significance in acute coronary syndromes and the relationship between IMA levels and coronary artery lesions in patients with coronary artery disease(CAD); and to make researches on the N-terminal structure of IMA to evaluate its formation mechanism.Methods ACB test was established for the detection of IMA levels, and the precision, sensitivity, specificity, cutoff value and some influential factors of IMA were evaluated. 1086 serum specimens were detected, including 729 healthy persons as controls, 182 patients with acute coronary syndromes(ACS), 145 patients who underwent coronary angiography(CAG) and 30 patients with acute cerebral ischemia. Cardiac troponin I (cTnI) levels of the same patients with ACS and those undergoing CAG were assayed by immumofluorescence method. IMA was purified by salting out and ion exchange chromatography. Then the purified protein was taken to analyze by mass spectrometry, N-terminal sequencings and circular dichroism (CD) spectra measurement.Results (1) The intra-assay CV of ACB test was 4.74%, and inter-assay CV was 6.29%. Linearity of the ACB test was over a concentration range of 20-60 g/L, and the correlation coefficient was 0.982. The absorbances of IMA tested from EDTA anticoagulant plasma were significantly lower than those tested from serum and heparinized plasma(P<0.05).(2) The IMA levels in 729 healthy persons as controls were 0.318±0.081 absorbance units(ABSU). There were no significant gender or age differences in...