👤 Christa M Cobbaert

Apolipoprotein standardization in multiple calibration laboratories requires equivalent results to value assign matrix-based reference and external quality assurance materials. A multiplexed LC-MS/MS-based reference measurement procedure (RMP) has been developed for serum apolipoproteins apo(a), apoA-I, apoB, apoC-I, apoC-II, apoC-III, and apoE. This study evaluates the transferability of the RMP between 3 calibration labs and determines the between-laboratory imprecision. Six periodic ring trial surveys were held. The study protocol, calibrators, internal standards, quality controls (QCs), and clinical samples (CSs) were shared among the laboratories. Intra-laboratory imprecision and inter-peptide comparisons evaluated intra-laboratory performance, while inter-laboratory imprecision evaluated equivalence between the calibration labs. Precision of the common bilevel QC monitored the level of harmonization over time. Intra-laboratory imprecision fulfilled predefined analytical performance, defined as repeatability <50% of the maximum allowable uncertainty (MAU) at minimal criteria. Median interlaboratory variation (CVbl) was 3.71%, 3.33%, 7.38%, 6.74%, 3.88%, and 3.90% for apoA-I, apoB, apoC-I, apoC-II, apoC-III, and apoE, respectively. For apo(a), CVbl was concentration (x) dependent following 206.32×x-0.899%. In QC samples, the average imprecision for all apolipoproteins decreased from 6.0% and 18.1% for QC1 and QC2, to 5.2% and 9.5%, indicating improvement of analytical performance of the network over time. This study shows the feasibility of transferring the multiplex apo LC-MS/MS-based RMP between laboratories. Predefined performance specifications were fulfilled for all seven apolipoproteins. Ongoing round-robin studies will ensure stable performance of the calibration labs required to accomplish an accurate value-base for apolipoprotein certification of commercial reagents. Show less

Lipoprotein(a) (Lp(a)) has the reputation of being the most misunderstood metric in laboratory medicine. The unique apolipoprotein(a) (apo(a)) in Lp(a) is very heterogenous, the kringle IV domain of apo(a) being formed by 12-50 kringles due to 3 to ∼40 KIV Show less

Oxidized phospholipids on apolipoprotein B-100 (OxPL-apoB) reflect pro-inflammatory properties of Lp(a) (lipoprotein(a)). The effect of OxPL-apoB on major adverse cardiovascular events (MACE) in patients with acute coronary syndrome in recent the era is not known. OxPL-apoB levels and Lp(a) were measured in 11 630 participants before and 5185 participants 4 months after randomization to alirocumab or placebo in the ODYSSEY OUTCOMES trial. Proportional hazards models adjusted for baseline covariates evaluated associations between log Participants were followed for a median 2.9 years; the median age was 58 years, and 23.9% were female. Alirocumab reduced median placebo-adjusted OxPL-apoB by 13.0% and Lp(a) by 26.2% (both In patients with recent acute coronary syndrome receiving optimized statin treatment, elevated OxPL-apoB levels predicted MACEs, a relationship abrogated by alirocumab. The interaction of OxPL-apoB and Lp(a) in the placebo group indicates that OxPL-apoB independently predicts MACEs when Lp(a) levels are relatively low. URL: https://www.clinicaltrials.gov; Unique identifiers: NCT001747 and NCT01663402. Show less

Residual cardiovascular risk remains, despite achieving low-density lipoprotein cholesterol targets with high-intensity statins. Traditional risk scores are suboptimal. This study evaluated the prognostic utility of a 9-plex apolipoprotein panel in recent patients with acute coronary syndrome on statins and its role in predicting treatment benefit by alirocumab, a PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitor, enabling precision medicine. Baseline serum samples from 11 843 participants in the ODYSSEY OUTCOMES trial (https://www.clinicaltrials.gov; Unique identifier: NCT01663402) were analyzed using mass spectrometry to measure Apo(a), ApoA-I, ApoA-II, ApoA-IV, ApoB, ApoC-I, ApoC-II, ApoC-III, and ApoE. Using logistic regression, probabilities of major adverse cardiovascular events (MACE) and all-cause death over a median follow-up of 2.9 years were estimated based on baseline apolipoproteins and lipid concentrations. Clinical performance was assessed by comparing the area under the curve (AUC) of 3 models: the apolipoprotein panel, the lipid panel (total cholesterol, high-density lipoprotein cholesterol, and triglycerides), and a combination. In addition, prediction models estimating the treatment benefit of alirocumab by the apolipoprotein panel were developed. The prognostic performance of the apolipoprotein panel for MACE showed an AUC (95% CI) of 0.648 (0.626-0.670), compared with 0.579 (0.557-0.602) for the lipid panel. For all-cause death, the apolipoprotein panel had an AUC of 0.699 (0.664-0.733), while the lipid panel had an AUC of 0.599 (0.564-0.635). Adding the apolipoprotein panel significantly improved the performance of the conventional lipid panel ( A multiplex apolipoprotein panel led to better prediction of MACE and all-cause death, beyond lipids, in patients with postacute coronary syndrome on optimized statin therapy. The panel also predicts the treatment benefit of alirocumab. Further validation of this approach is now needed, and if confirmed and improved, it could lead to better disease prediction and management in the future. Show less

Apolipoprotein (Apo) C3 has been associated with incident coronary heart disease and major adverse cardiovascular events (MACE). Whether ApoC3 levels predict risk in patients with acute coronary syndrome (ACS) on optimized statin treatment is unknown. ApoC3 was measured by mass spectrometry at baseline (n=11,956) and after 4 months' treatment (M4; n=11 176) with alirocumab or placebo in the ODYSSEY OUTCOMES trial. Patients with fasting triglycerides >400 mg/dL were excluded. The association of baseline ApoC3 with risk of MACE or death was assessed in post hoc adjusted Cox regression models and spline analyses adjusted for treatment and ApoB. In adjusted models in the alirocumab group we determined association of ApoC3 change from baseline to M4 with subsequent risk of MACE and death. Median (Q1, Q3) baseline ApoC3 concentration was 85 (65, 113) mg/L. With adjustment for ApoB, baseline ApoC3 showed no clinically meaningful relationship to risk of MACE or death in spline analyses and no association with MACE (P=0.89) or death (P=0.70) in Cox regression analyses. Alirocumab reduced ApoC3 modestly by median -10 (-27, -5) mg/L (P<0.0001) and reduced MACE (10.1% vs 12.1%; P=0.0006) and death (3.5% vs 4.2%; P=0.045) versus placebo. However, the change in ApoC3 on alirocumab did not predict subsequent MACE or death. In patients with recent ACS on optimized statins without severe hypertriglyceridemia, neither baseline ApoC3 (accounting for ApoB) nor ApoC3 change with alirocumab predicted MACE or death. It is uncertain whether targeted therapies producing larger reductions in ApoC3 from higher baseline levels will affect cardiovascular risk. Show less