Discriminant ratio and biometrical equivalence of measured vs. calculated apolipoprotein B(100) in patients with T2DM

BACKGROUND: Apolipoprotein B(100) (ApoB(100)) determination is superior to low-density lipoprotein cholesterol (LDL-C) to establish cardiovascular (CV) risk, and does not require prior fasting. ApoB(100) is rarely measured alongside standard lipids, which precludes comprehensive assessment of dyslipidemia. OBJECTIVES: To evaluate two simple algorithms for apoB(100) as regards their performance, equivalence and discrimination with reference apoB(100) laboratory measurement. METHODS: Two apoB(100)-predicting equations were compared in 87 type 2 diabetes mellitus (T2DM) patients using the Discriminant ratio (DR). Equation 1: apoB(100) = 0.65*non-high-density lipoprotein cholesterol + 6.3; and Equation 2: apoB(100) = −33.12 + 0.675*LDL-C + 11.95*ln[triglycerides]. The underlying between-subject standard deviation (SD(U)) was defined as SD(U) = √ (SD(2)(B) - SD(2)(W)/2); the within-subject variance (V(w)) was calculated for m (2) repeat tests as (V(w)) = Σ(x(j) -x(i))(2)/(m-1)), the within-subject SD (SD(w)) being its square root; the DR being the ratio SD(U)/SD(W). RESULTS: All SD(u), SD(w) and DR’s values were nearly similar, and the observed differences in discriminatory power between all three determinations, i.e. measured and calculated apoB(100) levels, did not reach statistical significance. Measured Pearson’s product-moment correlation coefficients between all apoB(100) determinations were very high, respectively at 0.94 (measured vs. equation 1); 0.92 (measured vs. equation 2); and 0.97 (equation 1 vs. equation 2), each measurement reaching unity after adjustment for attenuation. CONCLUSION: Both apoB(100) algorithms showed biometrical equivalence, and were as effective in estimating apoB(100) from routine lipids. Their use should contribute to better characterize residual cardiometabolic risk linked to the number of atherogenic particles, when direct apoB(100) determination is not available.