Statistical Issues for Genotyping Blood Pressure Sensitivity to Weight Loss and Sodium Diet in the Elderly

• Activity Number: 657
• Type: Contributed
• Date/Time: Thursday, August 2, 2012 : 10:30 AM to 12:20 PM
• Sponsor: Biometrics Section
• Author(s): Jie Liu*+ and Jerry Cheng and Javier Cabrera and John Kostis and William Kostis
• Companies: Rutgers University and Robert Wood Johnson Medical School and Rutgers University and Robert Wood Johnson Medical School and General Hospital of Boston
• Keywords: Clinical trials ; Gene polymorphism ; Recursive partitioning algorithm

Abstract

This work analyzed the Trial of Non-pharmacologic Interventions in the Elderly, a randomized observer blind clinical trial for hypertensives. The patients were randomized to get intensive intervention in weight reduction, dietary sodium reduction, both reductions, or attention control. We examined the relationship of 21 gene polymorphisms previously found to be associated with hypertension, diabetes, or obesity, with the change in blood pressure. We used a recursive partitioning algorithm which selected genotypes for which the effect of weight change or sodium change on the blood pressure response was different than that in the population. Unique binary splitting of observations based on genotypes was chosen. To test for the difference in the effects between the total data set and subgroups, we found the distribution of the difference of the estimates in question due to dependence. This statistic was used to rank the different genotypes to decide their biological relevance. We applied a simple form of the distribution and found that patients with certain genotypes treated with weight reduction or sodium reduction had significant different sensitivity from the overall population.