Lipoprotein(a) immunoassays and their associations with coronary artery calcification and aortic valve calcification

Background: Lp(a) causes atherosclerosis and degenerative aortic valve disease, but concerns have risen that mass-based assays may beaffected by isoform sizes and provide inaccurate estimates of Lp(a) exposure. Methods: We compared contemporary immunoturbidimetric assays reporting either mass-based (Randox) or molar-based (Roche) using data from 5,129 unselected participants from the prospective population-based Rotterdam Study cohort. We studied the association of both Lp(a) measurements with the burden of coronary artery calcium (CAC) and aortic valve calcification (AVC) in a random subset of participants who underwent cardiac CT. Results: There was a near perfect linear correlation between Lp(a) concentrations from both immunoassays (R² 98.8%) with most pronounced differences apparent only at very high Lp(a) concentrations. Lp(a) concentrations were related with natural logtransformed Agatston scores (Randox standardized linear β 0.1003, P = 5.6·10⁻⁸; Roche standardized linear β 0.1004, P = 5.4·10⁻⁸). Lp(a) concentrations were strongly but similarly related to natural log-transformed AVC Agatston scores (Randox standardized linear β 0.1525, P = 9.2·10⁻¹⁶; Roche standardized linear β 0.1539, P = 4.8·10⁻¹⁶). Conclusion: We demonstrate that these immunoassays provide interchangeable Lp(a) measurements, and that associations with CAC and AVC were near-identical. This provides opportunities to directly compare findings from research done with either immunoassay. Trial Registration: The Rotterdam Study has been entered in the Netherlands National Trial Register and the WHO International Clinical Trials Registry Platform under shared catalog number NTR6831.