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Select Contemporary Statistical Concepts in Heart Failure Clinical Trials: Insights From the Heart Failure Collaboratory.

Evolving statistical concepts and innovative trial designs for heart failure (HF) clinical trials seek to improve the conduct, efficiency, and likelihood of meaningful evidence generation crucial for advancing therapeutic development and optimizing patient care. HF trials with conventional statistical frameworks often require large sample sizes, long follow-up times, and high cost to generate sufficient evidence. Novel statistical methodologies would be of interest if they could address these issues while retaining or enhancing the clinical relevance and reliability of results. The HFC (Heart Failure Collaboratory), comprising clinical investigators, clinicians, statisticians, patients, government representatives, payors, and industry collaborators, leads efforts to improve HF research methodologies. HFC discussions have included statistical concepts such as the estimand framework, HR drift, and analytic methods, including the win ratio and restricted mean survival time, that have not been used frequently in HF trials. The estimand framework encourages precise definition and alignment of trial objectives with trial design. The win ratio method attempts to incorporate and prioritize multiple clinically meaningful outcomes by using a hierarchy of clinical importance. The restricted mean survival time provides an alternative to the HR as a measure of therapeutic effect by quantifying the mean time gained or lost during a fixed time after randomization. This paper provides a critical review of some evolving HF trial design methodologies and statistical concepts for the HF community as discussed within the HFC. Our goal is to foster collaboration among diverse stakeholders and advance the development of effective treatments and improve patient care outcomes.

Heart Failure

Nuclear protein changes in rat hepatomas correlating with growth rate.

The nature of nuclear proteins that are soluble in 8 M urea-50 mM phosphate, pH 7.6, was compared in rat liver and Morris hepatomas, Isoelectric focusing, using carrier ampholytes for a pH gradient of 3.5 to 10, indicated that with increasing growth rate of the hepatomas there was a progressive tendency for a decrease in nonhistone nuclear proteins with isoelectric points in the range 7.5 to 8.9 and an increase in the range 5.1 to 6.7. Studies on the influence of time on the pH gradient revealed that a nonuniform drift provided a better resolution of the pH range 7.5 to 8.9 at 7 hr than at 24 hr, while the latter time for electrofocusing gave an improved resolution of the pH range 5.1 to 6.7 Polyarcylamide gel electrophoresis in a urea-acetic acid system showed that 8 M urea-50 mM phosphate; pH 7.6 extracted a small part of the histones from nuclei of both liver and hepatomas. There was less extraction of histones from the hepatoma nuclei, especially in two rapidly growing hepatomas with the most notable difference being seen in the lysine-rich H1 histone. The results suggested that in addition to qualitative or quantitative changes in nonhistone nuclear proteins in liver cancer there are alterations in the binding of histones to chromatin.

Acetates

pH gradient electrophoresis and isoelectric focusing of lipoproteins on agarose bead thin layers.

A new method of isoelectric focusing (IEF) and pH gradient electrophoresis, using thin layers of agarose gel beads, was devised to investigate chylomicrons and very low density lipoproteins (VLDL). pH gradient stability and cathodal gradient drift were similar to those of polyacrylamide gel IEF, and linearity of gradients was maintained for 23 hr. Chylomicrons and VLDL were detectable without staining. Chylomicrons from human serum and from rat lymph migrated in this system. Rat lymph chylomicrons, obtained by ultracentrifugation, migrated in several discrete bands, and this heterogeneity or rat chylomicrons was confirmed by electron microscopic demonstration of chylomicrons in each band. This new technique has permitted the first measurement of isoelectric points of some lipoproteins in the ultracentrifuged fraction of human serum chylomicrons and the first separation of multiple discrete fractions of ultracentrifuged lymph chylomicrons.

Animals

Population structure and genetic heterogeneity in the Upper Markham Valley of New Guinea.

An analysis is presented of the standardized Wahlund's variances (f) in gene frequencies of the ABO, Rh and MNS blood group systems among 19 villages of the Atsera isolate of the upper Markham Valley, Papua New Guinea. In the past, there has been some disagreement over the relative importance of population structure and natural selection in the determination of these variances. The Lewontin-Krakauer test is presented as a means of resolving this disagreement. According to this test, selectively neutral variation in gene frequencies should generate essentially homogeneous values of f for all loci, a homogeneity which can be tested by comparing the value of (formula: see text) to a theoretical (formula: see text) expected when variations in (formula: see text) are due solely to sampling error. The observed value of (formula: see text) for the Atsera isolate is 2.9 x 10(-5), which is not significantly different from the expected values that range from 1.23 x 10(-5) to 2.46 x 10(-5) depending on the constant used in calculating (formula: see text). Therefore it appears that nonselective aspects of population structure such as genetic drift and intervillage migration are responsible for the recorded genetic variation in this isolate.

ABO Blood-Group System

Population genetics in the province of Ferrara. I. Genetic distances and geographic distances.

The ABO and Rh systems of the population in 26 residential units in the province of Ferrara were studied to detect the effect of genetic drift on the differentiation of gene frequencies. Results obtained from principal components analysis and dendrograms were similar. A significant correlation between genetic and geographic distance was found. It was therefore hypothesized that in the area of Ferrara children born to parents originating from different communes were heterozygous at more loci than children born to parents originating from the same commune. It was also thought that it may be possible to use geographic distance between birthplaces of parents as an indicator of hybridity in their children.

ABO Blood-Group System