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Evaluation of the albumin cobalt binding (ACB) assay for measurement of ischaemia-modified albumin ( |
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Evaluation of the albumin cobalt binding (ACB) assay
for measurement of ischaemia-modified albumin (IMA) on the Beckman
Coulter LX-20.
Ann Clin Biochem. 2006 Nov;43(Pt 6):494-9.
Maguire OC, O'Sullivan J, Ryan J, Cunningham SK.
Clinical Biochemistry Department, St Vincent's University Hospital, Elm Park, Dublin 4, Ireland.
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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.
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