Analytical Validation of Direct Lipoprotein(a)-Cholesterol Assay

Accurate measurement of lipoprotein(a) cholesterol [Lp(a)-C] may be useful in interpreting the traditional lipid panel, particularly in patients with high Lp(a). We developed and analytically validated in a CLIA certified laboratory a direct immunocapture ELISA for quantifying Lp(a)-C in human plasma using an apolipoprotein(a)-specific monoclonal antibody (LPA4) coupled to magnetic beads. The linearity of the assay was found to be excellent (R2=1.00), with % Bias ranging from 0.3% (upper limit of quantification) to 16.1% (low limit of quantification) and %CV ranging from 3.4% to 16.2%. The analytical measuring range was 0.78 mg/dL to 40.0 mg/dL and the limit of Blank and limit of Detection were 0.02 mg/dL and 0.05 mg/dL, respectively. The intra- and inter-assay coefficients of variation determined on four quality control samples, ranged from 4.9% to 7.6% and from 12.6% to 15.0%, respectively. No interference was observed from hemolysis (up to 0.71 g/dL), bilirubin (up to 10.1 mg/dL), or triglycerides (up to 1082 mg/dL. Lp(a)-C was stable for at least 3 months at -70 °C and through two freeze-thaw cycles. Direct Lp(a)-C correlated strongly with Lp(a) molar (r=0.93, p<0.001) concentration. This study reports the results of the first analytical validation of a direct method to quantify Lp(a)-C, enabling standardized quantification of Lp(a)-C suitable for research studies and clinical trials; additional clinical outcome validation will be required prior to routine clinical implementation.