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Atherosclerosis. 2019 Oct;289:206-213. doi: 10.1016/j.atherosclerosis.2019.08.015. Epub 2019 Aug 27.

Comparison of lipoprotein (a) serum concentrations measured by six commercially available immunoassays.

Author information

1
Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Graz, Austria. Electronic address: hubert.scharnagl@medunigraz.at.
2
Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Graz, Austria.
3
Department of Laboratory Medicine, Konventhospital Barmherzige Brueder, Linz, Austria.
4
Institute of Genetic Epidemiology, Department of Genetics and Pharmacology, Medical University of Innsbruck, Innsbruck, Austria.
5
Institute of Molecular Biology and Biochemistry, Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging Medical University of Graz, Austria.
6
Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Graz, Austria; Medical Faculty Mannheim, University of Heidelberg, Germany; SYNLAB Academy, SYNLAB Holding Deutschland GmbH, Mannheim and Augsburg, Germany.
7
Mannheim Institute of Public Health, Social and Preventive Medicine, Medical Faculty Mannheim, University of Heidelberg, Germany.

Abstract

BACKGROUND AND AIMS:

Lipoprotein (a) [Lp(a)] is an established causal risk factor for cardiovascular disease (CVD), independently of low-density lipoproteins (LDL) and other risk factors. The recognition of Lp(a) as an atherogenic molecule has raised the demand for reliable quantification methods in the clinical laboratory. The aim of this work is to compare commercial immunochemical assays.

METHODS:

We measured Lp(a) serum concentrations using six different assays, providing Lp(a) in mg/dl (Denka Seiken, Abbott Quantia, Beckman, Diasys 21FS, and Siemens N Latex) or in nmol/l (Roche TinaQuant, Diasys 21 FS) in 144 serum samples covering the clinically relevant range of Lp(a) concentrations. All assays relied on five-point calibrations using calibrators provided by the manufacturers. Apolipoprotein(a) phenotyping was performed by sodium dodecyl sulfate-agarose gel electrophoresis (SDS-agarose) followed by immunoblotting.

RESULTS:

Most bivariate correlation coefficients were greater than 0.90. Compared to an established IFCC-proposed reference material, the results of the different assays diverged from the target values (43.3 mg/dl or 96.6 nmol/l) by -8% (Siemens N Latex) and +22% (Abbott Quantia). Stratification of the samples into five groups with increasing Lp(a) concentrations and difference plots showed that the differences among assays were concentration-dependent. Some assays overestimated Lp(a) at high concentrations compared to the Denka Seiken assay.

CONCLUSIONS:

Current commercial immunological assays for measuring Lp(a) concentrations are differently calibrated. Their biases differ significantly across the clinically relevant concentration range in a non-linear manner. This is not conclusively explained by apolipoprotein (a) phenotypes. Further international efforts to harmonize assays for Lp(a) are needed.

KEYWORDS:

Atherosclerosis; Harmonization; Lipoprotein (a) assays; Myocardial infarction

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