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Performance of Five Lipoprotein(a) Immunoassays Evaluated

By LabMedica International staff writers
Posted on 06 Apr 2021
Increased serum Lipoprotein(a) [Lp(a)] is considered an independent, inherited risk factor for atherosclerotic cardiovascular disease (ASCVD), including myocardial infarction and stroke. This risk is believed to be due to pro-atherogenic, pro-inflammatory, and pro-thrombotic properties of the Lp(a) particle.

Lp(a) can be measured using a variety of methods, including enzyme linked immunosorbent assays (ELISA), latex-agglutination, immunoturbidimetry/immunonephelometry, electrophoresis, and immunofixation electrophoresis (IFE). A confounding factor is that Lp(a) can be reported in either mass units (mg/dL of the total Lp(a) particle) or molar concentration of particles (nmol/L).

Image: The Diazyme Lipoprotein A assay kit is for the in vitro quantitative determination of Lp(a) concentration in human serum or plasma on Clinical Chemistry Systems (Photo courtesy of Diazyme)
Image: The Diazyme Lipoprotein A assay kit is for the in vitro quantitative determination of Lp(a) concentration in human serum or plasma on Clinical Chemistry Systems (Photo courtesy of Diazyme)

Medical Laboratorians at the ARUP Institute of Clinical and Experimental Pathology (Salt Lake City, UT, USA) and their colleagues used 80 residual serum samples, and specimens from 120 self-reported healthy subjects (61 females/59 males) were also tested in a study. The aim of the study was to evaluate performance characteristic of five different Lp(a) assays using the cobas c501 analyzer (Roche Diagnostics, Indianapolis, IN, USA).

The five assay for Lp(a) used were from: Diazyme (Poway, CA, USA), Kamiya Biomedical Company (Seattle, WA, USA), MedTest Dx (Canton, MI, USA), Randox Laboratories (Crumlin, UK) and Roche Diagnostics, configured to mg/dL units. Assays from Diazyme and Kamiya were also configured using nmol/L units in separate studies. Studies included sensitivity, imprecision, linearity, method comparison, and evaluation of healthy subjects. Imprecision (intra-day, 20 replicates; inter-day, duplicates twice daily for five days) and linearity were evaluated using patient pools. Linearity assessed a minimum of five patient splits spanning the analytical measurement range (AMR).

The scientists reported that all methods met manufacturer claims regarding sensitivity: observed (manufacturer claim): Diazyme, 0.7 mg/dL (1.3 mg/dL); Kamiya, 1.2 mg/dL (5.0 mg/dL); MedTest, 0.2 mg/dL (1.3 mg/dL); Randox, 0.7 mg/dL (3.0 mg/dL); Roche, 0.3 mg/dL (4.0 mg/dL). Lp(a) assays also demonstrated acceptable imprecision and met manufacturers’ claims, with CVs less than 6% in all cases. Imprecision studies demonstrated %CVs ranging from 2.5 – 5.2% for the low pool (average concentration from 7.3 – 12.4 mg/dL); high pool %CVs ranged from 0.8 – 3.0% (average concentrations from (31.5 – 50.2 mg/dL). Linearity was confirmed for all assays. Variation in accuracy was observed when comparing results to an all method average. Lp(s) results were higher in females versus males in self-reported healthy subjects.

The authors concluded that all assays performed according to manufacturer described performance characteristics, although differences were observed across Lp(a) assays tested when compared to an all method average. The study was published on March 24, 2021 in the journal Practical Laboratory Medicine.

Related Links:
ARUP Institute of Clinical and Experimental Pathology
Roche Diagnostics
Kamiya Biomedical Company
MedTest Dx
Randox Laboratories

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