Concordance between plasma apolipoprotein B levels and cholesterol indices among patients receiving statins and nonstatin treatment: Post-hoc analyses from the U.K. InPractice study

BACKGROUND: Apolipoprotein B (ApoB) is a superior predictor of low-density-lipoprotein (LDL) particle number and cardiovascular disease (CVD) risk compared with LDL-cholesterol (LDL-C) levels. Current evidence has shown a degree of discordance between LDL-C with ApoB levels among patients not receiving lipid-lowering therapy. The extent of this discordance among patients receiving LDL-lowering therapies however is less clear. METHODS: We performed a post hoc analysis of the InPractice data looking at the concordance between LDL-C, non-high density lipoprotein-cholesterol (nonHDL-C) and total cholesterol with ApoB values. The study involved 786 high-risk CVD patients from 34 primary care centers initially treated with simvastatin (S) 40 mg at baseline subsequently randomized to adding ezetimibe 10 mg to S 40 mg (E/S40) or changed to atorvastatin (A) 40 mg or to rosuvastatin (R) 5-10 mg for 6 weeks. RESULTS: At 6 weeks after treatment, the association between LDL-C and ApoB values for the different treatment regimes were similar; Pearson's correlation coefficients between LDL-C and ApoB were 0.84 (E/S40), 0.82 (A), and 0.83 (R). Overall, ApoB appeared to have a slightly greater correlation with nonHDL-C than with LDL-C across all treatment groups, for baseline and posttreatment values. The analysis of quintile frequencies showed a similar pattern; the proportion of patients who had values that fell in the same quintile post treatment for ApoB and LDL-C levels were 52.2% (E/S40), 44.5% (A), and 49.4% (R). Concordance between ApoB and nonHDL-C was 60.6% (E/S40), 62.4% (A), and 61.8% (R). Kappa analysis confirmed fair agreement between LDL-C and ApoB levels for all treatment groups; 0.59 (E/S40), 0.54 (A), and 0.56(R). CONCLUSION: We showed that the association between ApoB and LDL-C is similar across different lipid-lowering treatment regimes, which suggests that the use of different lipid-lowering agent confers similar ability to predict ApoB levels. When determining CVD risk at an individual patient level, limitation exists when using LDL-C or nonHDL-C per se as risk markers. In the absence of ApoB measurement, we believe that information from both LDL-C and nonHDL-C should be used together to improve the estimation of residual CVD risk among patients who are already receiving lipid lowering therapy. (C) 2011 National Lipid Association. All rights reserved.