Abstract
Abstract Background Lipoprotein (a) (Lp(a)) is an independent risk factor for cardiovascular disease. Because of the polymorphism of Apolipoproteine-A (Apo A), a component of LP(a) which is under tight genetic control, two main isoforms of Lp(a) exist and are responsible for a wide inter-individual variability. Despite Lp(a) levels are genetically determined, a single measurement during an entire life span may suffice for this purpose. However, this is not unequivocal, since several non genetic factors may be responsible for the natural variability of Lp(a) within individuals. Aims To characterize the reproducibility of Lp(a) levels; to determine the influence of several non genetic factors (inflammation, chronic kidney failure, chronic hepatic failure, dysthiroidism, hormonal status, Niacine treatment) on the natural Lp(a) variability within subjects. Methods Between 2004 and 2014, 15 815 Lp(a) measurements were performed by immunoturbidimetry in a reference center for 48 belgian laboratories in 11 982 subjects. 2049 individuals underwent 1 to 20 consecutive Lp(a) samplings. Reproducibility of the last Lp(a) measurement was compared to the previous one in term of time. The influence of non genetic factors on Lp(a) natural variability was studied on 300 patients randomly selected. Results Higher Lp(a) levels at the first measurement elicited additional Lp(a) determinations in subsequent measurements (p<0.0001). Lp(a) measurement became less reproducible when exceeding ± 35 mg/dL. There is a strong association between two consecutive Lp(a) measurements (r=0.85, p<0.0001). A significant but weak correlation has been found between Lp(a) and CRP levels (r=0.17, p=0.008) and the time intervals between two consecutive measurements (r=0.07, p<0.0001). No correlations have been found between Lp(a) levels and others non genetic factors said above. Niacine treatement and menopause with hormonal therapy replacement are responsible for a reduced median Lp(a) level (p=0.04, p=0.02, respectively). Conclusion Lp(a) levels are poorly reproducible when Lp(a) levels are elevated: the higher the Lp(a) levels at the first measurement, the higher the variability between consecutive measurements. Non genetic factors such as inflammation, hormonal status, timing of sampling seem to influence the Lp(a) levels but a causal link cannot be stated. Funding Acknowledgement Type of funding source: Public grant(s) – EU funding. Main funding source(s): Fonds Erasme, FNRS_Fonds National pour la Recherche Scientifique
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