Usefulness of apolipoprotein B/apolipoprotein A-I ratio to predict coronary artery disease independent of the metabolic syndrome in African Americans

Abstract

Studies have demonstrated that the apolipoprotein B/apolipoprotein A-I (apoB/apoA-I) ratio predicts cardiovascular risk better than any of the cholesterol indexes. A number of factors that define the metabolic syndrome (MS) differ across African-American and European-American ethnicities. We assessed the relation of the apoB/apoA-I ratio to MS and coronary artery disease (CAD) in 224 African Americans and 304 European Americans. The MS was defined using the revised National Cholesterol Education Program Adult Treatment Panel III criteria, and CAD was assessed as ≥50% stenosis or a continuous cardiovascular score (0 to 75). The European Americans had a greater apoB/apoA-I ratio than the African Americans (1.15 vs 1.07, p = 0.008). The apoB/apoA-I ratio was associated with presence of the MS in both European Americans (odds ratio 5.9, 95% confidence interval 2.53 to 13.57, p <0.001) and African Americans (odds ratio 8.3, 95% confidence interval 3.52 to 19.25, p <0.001) and was greater in subjects with the MS than in those without the MS (1.21 vs 1.04, p <0.001, for European Americans and 1.20 vs 0.94, p <0.001, for African Americans). A stepwise increase was seen in the prevalence of the MS across the apoB/apoA-I ratio tertiles in both ethnic groups (chi-square = 13.1, p <0.001, for European Americans and chi-square = 19.6, p <0.001, for African Americans). On multiple regression analyses, the apoB/apoA-I ratio independently predicted CAD in African Americans (β = 0.242, p = 0.011). The cardiovascular score was significantly increased across the apoB/apoA-I ratio tertiles in the European-American subjects with the MS (p = 0.001). However, this association was seen in the African-American subjects without the MS (p = 0.023). In conclusion, the apoB/apoA-I ratio differed across ethnicities and was associated with presence of the MS in both groups. Among African Americans, an elevated apoB/apoA-I ratio independently predicted a greater risk of CAD.

Figure 1

ApoB/apoA-I ratio in subjects with and without MS across ethnic groups. *: P<0.001

Figure 2

Prevalence of MS across apoB/apoA-I ratio tertiles among European-Americans and African-Americans. The cut-off points for tertiles were ≤0.98, 0.98–1.26, ≥1.26 for European-Americans and ≤0.88, 0.88–1.20, ≥1.20 for African-Americans, respectively. The results are based on n=99 for 1^st, n=103 for 2^nd and n=100 for 3^rd tertiles in European-Americans and n=76 for 1^st, n=74 for 2^nd and n=74 for 3^rd tertiles in African-Americans. Two European-American subjects (1 with and 1 without MS) were excluded from the analyses due to missing data.

Figure 3

Composite cardiovascular scores across apoB/apoA-I ratio tertiles among European-Americans (A) and African-Americans (B) with and without MS. ApoB/apoA-I tertiles were based on all subjects within each ethnic group and the numbers were (A) n=51 for 1^st, n=73 for 2^nd and n=74 for 3^rd tertiles for subjects with MS and n=48 for 1^st, n=30 for 2^nd and n=26 for 3^rd tertiles for subjects without MS among European-Americans; (B) n=23 for 1^st, n=38 for 2^nd and n=49 for 3^rd tertiles for subjects with MS and n=53 for 1^st, n=36 for 2^nd and n=25 for 3^rd tertiles for subjects without MS among African-Americans. Two European-American subjects (1 with and 1 without MS) were excluded from the analyses due to missing data. *: P=0.001.