PubMed · 14963265
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B Panayiotou, M Fotherby. 2004-02-12. The ACCESS study.. https://doi.org/10.1161/01.str.0000117970.06113.01
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In a traditional pharmacokinetics (PK), bioavailability (BA) /bioequivalence (BE) study, the same number of time points and sampling times are used for each subject. Often, an indirect inference is then made on some PK parameters such as area under the plasma concentration curve (AUC), maximum plasma concentration (C(max)), time to maximum plasma concentration (T(max)) or half-life. However, since these PK parameters are summarized from repeated measurements, a lot of information can be lost. The indirect inferences on some PK parameters are not always accurate. Taking the repeated measurements of the concentration curve into consideration, a functional linear model has been developed to compare concentration curves directly instead of the PK parameters. Considering the nature of repeated measurements, a multiple testing procedure is proposed to assess the equality of two concentration curves. A real data set is used to demonstrate the proposed procedure.
Standard intent-to-treat analyses of randomized clinical trials can yield biased estimates of treatment efficacy and toxicity when not all patients comply with their assigned treatment. Flexible methods have been proposed which correct for this by modelling expected contrasts between an individual's observed outcome and his/her potential outcome in the absence of exposure. Because such comparisons often require untestable assumptions, a sensitivity analysis is warranted. We show how this can be performed in a meaningful and practically useful way. Following the approach of Molenberghs, Kenward and Goetghebeur in a missing data context, we evaluate the separate contributions of structural uninformativeness and sampling variation to uncertainty about the population parameters. This leads us to consider Honestly Estimated Ignorance Regions (HEIRs) and Estimated Uncertainty RegiOns (EUROs), respectively. We use the results to estimate the causal effect of observed exposure on successful blood pressure reduction in a randomized controlled clinical trial with partial non-compliance.
Arterial hypertension (AH) is considered to be an important risk factor for vascular cognitive impairment and probably for Alzheimer's disease, too. In the current review we provide an overview of the major prospective clinical trials on this issue. With respect to the inconsistent findings of these studies one must state that the interrelations between AH and dementia are still incompletely understood. Regarding therapy there thus is a simple rule: AH should be treated until normal blood pressure values are reached. As long as the hypothesis of a J-curve between blood pressure and cognitive dysfunction has not been disproved, overaggressive blood pressure lowering cannot be recommended. Regarding the aim of preventing dementia, there is no evidence for the superiority of a specific antihypertensive treatment regimen.