Background: A role of inflammation for cardiovascular disease (CVD) is established. Lipoprotein(a), Lp(a), is an independent CVD risk factor where plasma levels are determined by the apolipoprotein(a), apo(a) gene, which contains inflammatory response elements.

Design: We investigated the effect of inflammation on allele-specific apo(a) levels in African Americans and Caucasians. We determined Lp(a) levels, apo(a) sizes, allele-specific apo(a) levels, fibrinogen and CRP levels in 167 African Americans and 259 Caucasians.

Results: Lp(a) levels were increased among African Americans with higher vs. lower levels of CRP (<3 vs. 3 mg/L) or fibrinogen (<340 vs. 340 mg/dl) levels (143 vs. 108 nmol/l, P=0.009, and 146 vs. 105 nmol/l, P=0.002, respectively). We next analyzed allele-specific apo(a) levels for different apo(a) sizes. No differences in allele-specific apo(a) levels across CRP or fibrinogen groups were seen among African Americans or Caucasians for small apo(a) sizes (<22 K4). Allele-specific apo(a) levels for medium apo(a) sizes (22–30 K4) were significantly higher among African Americans, with high levels of CRP or fibrinogen compared to those with low levels (88 vs. 67 nmol/l, P=0.014 and 91 vs. 59 nmol/l, P<0.0001, respectively). No difference was found for Caucasians.

Conclusions: Increased levels of CRP or fibrinogen are associated with higher allele-specific medium-sized apo(a) levels in African Americans, but not in Caucasians. These findings indicate that pro-inflammatory conditions results in a selective increase in medium-sized apo(a) levels in African Americans, and suggest that inflammation-associated events may contribute to the inter-ethnic difference in Lp(a) levels between African Americans and Caucasians.