Quality assurance measurement of the cholesterol markers apolipoproteins A1 and B; Going against the grain

Joannis Kinalis1,*, Eva Fahlen2, Erika Langenstam2, Erika Karabasic2

1Clinical Chemistry, 2Sahlgrenska University Hospital, Gothenburg, Sweden

Introduction: The apolipoproteins ApoB and ApoA1 are cholesterol markers for cardiovascular heart disease. Measurement of ApoB and ApoA1 is used to determine the need for cholesterol reducing medications such as statines to reduce the risk of future incidence of cardiovascular disease.

The method for analyzing ApoA1 and ApoB that was set up in the Clinical Chemistry laboratory during October 2009 did not concur with other methods from other laboratories. Also, samples from external control programs with known levels of ApoB and ApoA1 had too low levels in comparison to other methods. Which method was most accurate?

The link between the risk of acquiring cardiovascular disease and levels of ApoB and ApoA1 was studied in the Swedish Amoris study. With a sample size of 175 000 swedes, it forms the basis for the treatment limits indicated by the measured levels of ApoB and ApoA1 that are used when a doctor considers whether a patient should be treated with cholesterol reducing medicines. 

Objectives: The goal was to increase the accuracy of our analytical methods for Apolipoproteins.

Methods: We recalibrated our ApoB and ApoA1 analyses to match those of CALAB, the laboratory that performed the ApoB and ApoA1 analyses in the Amoris study. After contacting representatives of the Amoris study we calibrated our method against Northwest Lipid Metabolism And Diabetes Research Laboratories in Seattle, which had been used to calibrate the ApoB and ApoA1 methods at CALAB.

Results: While calibrating it was discovered that the company that set up the method had set the European values falsely too low. Also the company’s ApoA1 and ApoB calibrator value differed between the European and American versions. After our laboratory pressured them, the company now uses the same global calibration procedure of traceability and is also closely calibrated to the Amoris Study.

Conclusion: We believe this will lead to more accurate risk assessments since doctors will use ApoB and ApoA-1 results to decide appropriate cholesterol reducing treatments

Keywords: Biomarker, Cardiovascular