Multiplexed apolipoprotein profiling advances the assessment of residual lipid-related cardiovascular risk

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation

Background and Purpose

Low-density lipoprotein cholesterol (LDL-C) is among the conventional lipid parameters used to predict risk of cardiovascular disease (CVD). Statins lower blood levels of pro-atherogenic LDL-C, but a residual cardiovascular risk remains in some individuals with therapeutically optimised LDL-C levels. Although the metabolism of LDL-C and other lipoprotein particles is governed by a range of different apolipoproteins, only apolipoproteins A-I and B are measured in clinical assays. Using a more comprehensive apolipoprotein panel in a large epidemiological cohort, this study aimed to determine the association of individual apolipoprotein levels with risk of coronary heart disease (CHD).

Methods

Bottom-up multiple reaction monitoring–mass spectrometry (MRM–MS) was used in conjunction with stable isotope-labelled peptide standards to quantify plasma levels of 13 apolipoproteins in participants of the Precocious Coronary Artery Disease (PROCARDIS) study (N = 1916; 941 cases of CHD, 975 controls). The relationship between apolipoprotein levels and CHD was assessed after adjusting for established risk factors for CVD and correcting for statin use.

Results

The strongest positive associations with CHD in the PROCARDIS study were seen for triglyceride-related apolipoproteins C-I (odds ratio [OR] 2.38, 95% confidence interval [CI] 1.63–3.46), C-III (OR 2.95, 95% CI 1.85–4.71) and E (OR 2.35, 95% CI 1.54–3.58), as well as for apolipoprotein (a) (kringle IV type 2 repeat, OR 2.84, 95% CI 2.04–3.95). Comparing these with associations of apolipoproteins with CVD in the Bruneck study (N = 688) revealed consistency across the two cohorts. Robust inverse associations with CHD were observed for apolipoproteins A-IV (OR 0.45, 95% CI 0.31–0.65) and M (OR 0.29, 95% CI 0.19–0.44).

Conclusion

Analysing two large epidemiological cohorts, Bruneck and PROCARDIS, demonstrated that multiplexed apolipoprotein profiling improves the understanding of cardiovascular risk independent of conventional lipid parameters. Most prominently, triglyceride-related apolipoproteins were shown to positively associate with residual cardiovascular risk. The findings of this study support the need for development and implementation of standardised, MRM–MS-based apolipoprotein profiling assays to guide novel lipid-modifying therapies beyond statins.

Impact of adverse events on quality of life and hospital costs in secondary cardiovascular disease prevention

Background and purpose

People with atherosclerotic vascular disease remain at high risk of cardiovascular (CVD) events despite effective risk factor management 1. There is little research on impacts of adverse events on quality of life (QoL) and hospital cost to inform evaluations of novel interventions in this population. We estimate QoL and annual hospital costs associated with a range of adverse events of interests using the individual participant data from the Randomized Evaluation of the Effects of Anacetrapib through Lipid Modification (REVEAL) trial.

Methods

Data from the 30,449 participants with atherosclerotic vascular disease receiving effective statin therapy in REVEAL, were used to estimate regression models for participants' hospital costs and QoL using participants' characteristics at entry (socio-demographic, clinical, prior diseases and treatments) and time-updated adverse events. We estimate costs and QoL in the year of an event, and in subsequent years, using stepwise covariate selection (p-value <0.01). Standard errors were adjusted for clustering of participant annual costs.

Hospital episodes were costed (2019 UK£) using the UK Healthcare Resource Groups reference costs 2. One- and two-part generalized linear regression models (GLMs) for annual hospital costs (part 1: logistic model for estimating probability of incurring cost, part 2: GLM with Gaussian, Poisson or Gamma distributions with identity or log links for estimating costs, conditional on incurring any) were compared.

EQ-5D-5L questionnaires, completed by study participants at entry and final follow-up visits in the study, were mapped into QoL utility scores 3. QoL utility at final follow-up was used to estimate QoL decrements of adverse events using GLM linear model and adjusting for QoL at entry in addition to other participants characteristics.

Results

The two-part model with gamma distribution and identity link, indicated by specification tests and model fit statistics, was selected for modelling annual hospital costs (Figure 1). Non-haemorrhagic stroke, non-coronary revascularization, coronary revascularization and incident cancer were associated with highest hospital costs. The QoL model (Figure 2) indicated large QoL decrements associated with non-fatal non-haemorrhagic stroke, heart failure hospitalization, incident cancer and non-coronary revascularization, and comparatively small QoL decrement associated with experiencing non-fatal myocardial infarction.

Conclusion

These cost and QoL models in a well-managed contemporary high CVD risk patient population would assist in assessments of long-term net effects and cost-effectiveness of novel interventions to reduce cardiovascular risk.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Merck Sharp & Dohme and UK Medical Research Council Figure 1Figure 2

Assessments still win the day for me

In the November 23 issue, you published a letter from a nurse who questioned my preference for continuous assessment against state final examinations (Left in the lurch by continuous testing).

Parenteral nutrition in very low birth weight infants in the United Kingdom and Ireland

Parenteral nutrition (PN) plays an important role in providing nutrients for infants unable to tolerate enteral feeds study was to look at PN prescribing in neonatal units in the United Kingdom (U.K.) and Ireland, in particular in infants < 1.5 kg. A postal questionnaire was administered to the 235 neonatal units. The response rate was 179 (76%), of which 136 (76%) used PN. The initial amount of protein prescribed was 0.1-2 g/kg/day in 102 units (91%), >2 g/kg/day in 4 (4%) and 5 (5%) used no protein. 88 (80%) started lipids with the first PN prescription. Only 5 units (5%) started with >1 g/kg/day. The maximum dose of lipids and protein both varied from 2 - >4 g/kg/day. The initial glucose infusion rate was 4-8 mg/kg/min. Interestingly only 44% of units started PN in the first 24 hours of age. Hence results show great variation in PN prescribing.

Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables

Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.

Management of neonatal abstinence syndrome: a national survey and review of practice

AIM

To ascertain the present management of neonatal abstinence syndrome (NAS) in neonatal units in the United Kingdom (UK) and Ireland.

METHODS

Postal questionnaire to 235 neonatal units, with telephone follow-up of non-respondents.

RESULTS

The response rate was 90%, and 96% of respondents had a formal NAS guideline. The median number of infants treated annually for NAS was 6 (range 1-100). The method of Finnegan was the most widely used scoring system (52%). Morphine sulphate was the most commonly used first line agent for both opiate (92%) and polysubstance (69%) withdrawal. Dosing regimens varied widely. Units using a maximum daily morphine dose of <400 microg/kg/day were more likely to require the addition of a second agent (76% vs 58%, p = 0.027). Phenobarbitone was the drug of choice to treat seizures secondary to both opiate and polydrug withdrawal in 73% and 81% of units, respectively. 29% of units allowed infants to be discharged home on medication. 58% of these allowed administration of opiates in the community and in almost half of cases this was managed by a parent. Mothers on methadone whose serology was positive for hepatitis B and/or C were four times more likely to be discouraged from breastfeeding.

CONCLUSIONS

The majority of units currently use an opiate as the drug of first choice as recommended. Doses utilised and second agents added vary significantly between units. Many of our findings reflect the lack of high-quality randomised studies regarding management of NAS.