Biomedical subjects

Christine Pollicino

Publications and source records attributed to Christine Pollicino.

4 recordsLinked to original sources

PubMed2006

Guidelines for selecting among different types of bootstraps.

BACKGROUND: The bootstrap has become very popular in health economics. Its success lies in the ease of estimating sampling distribution, standard error and confidence intervals with few or no assumptions about the distribution of the underlying population. OBJECTIVE: The purpose of this paper is three-fold: (1) to provide an overview of four common bootstrap techniques for readers who have little or no statistical background; (2) to suggest a guideline for selecting the most applicable bootstrap technique for your data; and (3) to connect guidelines with a real world example, to illustrate how different bootstraps behave in one model, or in different models. RESULTS: The assumptions of homoscedasticity and normality are key to selecting the best bootstrapping technique. These assumptions should be tested before applying any bootstrapping technique. If homoscedasticity and normality hold, then parametric bootstrapping is consistent and efficient. Paired and wild bootstrapping are consistent under heteroscedasticity and non-normality assumptions. CONCLUSION: Selecting the correct type of bootstrapping is crucial for arriving at efficient estimators. Our example illustrates that if we selected an inconsistent bootstrapping technique, results could be misleading. An insignificant effect of controller treatment on total health expenditures among asthma patients would have been found significant and negative by an improperly chosen bootstrapping technique, regardless of the type of model chosen.

Confidence Intervals↗

PubMed2005

Neither plasma coenzyme Q10 concentration, nor its decline during pravastatin therapy, is linked to recurrent cardiovascular disease events: a prospective case-control study from the LIPID study.

Statins decrease LDL cholesterol and the risk of atherosclerotic cardiovascular disease (CVD). They also decrease coenzyme Q10 (CoQ10), an effect that may negate some of the statin benefit on CVD. We examined the relationship between plasma CoQ10 concentration and CVD in a prospective case-control study of the effect of pravastatin. Plasma samples from 250 LIPID trial patients who over 6 years suffered a recurrent CVD event (CVD death, nonfatal MI or stroke) and 250 matched controls who remained event-free for the same duration of follow-up were assayed for CoQ10 and lipids (cholesterol and cholesterylesters). Mean plasma CoQ10 concentrations were significantly lower in pravastatin-treated patients than in those assigned placebo (0.51 versus 0.60 micromol/L, P = 0.006), and there was a moderate correlation between CoQ10 and common cholesterylesters (Pearson correlation coefficients in patients randomised to placebo, range r = 0.42-0.63). Univariate conditional logistic regression did not suggest any relationship between plasma CoQ10 and the risk of future CVD events (odds ratio 1.18; 95% CI 0.74-1.87; P = 0.49). Instead, we observed a reduction in the rate of recurrent CVD events with increasing ratio of plasma cholesterylarachidonate to cholesteryllinoleate. This study confirms that pravastatin lowers plasma CoQ10 concentrations, but this does not appear to predict the risk of recurrent CVD events.

Cardiovascular Diseases↗

PubMed2005

Relation of diet to cardiovascular disease risk factors in subjects with cardiovascular disease in Australia and New Zealand: analysis of the Long-Term Intervention with Pravastatin in Ischaemic Disease trial.

BACKGROUND: Comparisons of the relation of diet with coronary heart disease (CHD) between countries with similar socioeconomic environments have been few. Patients in Australia and New Zealand (n = 9014) who participated in a large secondary prevention trial had significantly different CHD mortality rates. OBJECTIVE: The objective of this study was to ascertain the effects of nutrient consumption on cardiovascular disease risk in patients from the 2 countries. DESIGN: Nutrient consumption patterns were surveyed in a subgroup of 1077 patients on 3 occasions over 4 y during an intervention trial with a statin. RESULTS: Within the entire cohort of 9014 patients, the New Zealanders had significantly (40%) more cardiovascular deaths than did the Australians. In the subgroup of 1077 patients, the New Zealanders were found at entry to have eaten significantly more total (69.34 +/- 12.35 compared with 66.45 +/- 12.9 g/d) and saturated (26.23 +/- 8.41 compared with 24.37 +/- 7.36 g/d) fat (P < 0.001 for each) and to have significantly (4%) higher concentrations of LDL cholesterol (3.96 +/- 0.74 compared with 3.8 +/- 0.76 mmol/L; P < 0.001) than did the Australians. At baseline, patients with previous coronary artery bypass grafting had diets that were significantly different from those of patients without previous coronary artery bypass grafting. Relations between nutrients and plasma lipids confirmed the direct effects of saturated fatty acids on LDL cholesterol and of alcohol on plasma triacylglycerol and HDL cholesterol. Dietary counseling throughout the trial led to significant improvements in compliance with guidelines. However, neither the baseline nor the improved 1-y nutrient intakes predicted future changes in cardiovascular events. CONCLUSION: Differences in CHD mortality and in LDL-cholesterol concentrations between 2 populations with similar socioeconomic and cultural backgrounds were consistent with the amounts and types of fats eaten.

Aged↗

PubMed2002

Measuring health system resource use for economic evaluation: a comparison of data sources.

A key challenge for evaluators and health system planners is the identification, measurement and valuation of resource use for economic evaluation. Accurately capturing all significant resource use is particularly difficult in the Australian context where there is no comprehensive database from which researchers can draw. Evaluators and health system planners need to consider different approaches to data collection for estimating resource use for economic evaluation, and the relative merits of the different data sources available. This paper illustrates the issues that arise in using different data sources using a sub-sample of the data being collected for an economic evaluation. Specifically, it compares the use of Australia's largest administrative database on resource use, the Health Insurance Commission database, with the use of patient-supplied data. The extent of agreement and discrepancies between the two data sources is investigated. Findings from this study and recommendations as to how to deal with different data sources are presented.

Administrative Personnel↗