Using partial components to restore and use the concurrent validity of the Index of Readiness

In the presence of correlations among the dimensions of psychometric tests with summated scales, it is sometimes difficult to use the scores on the dimensions to predict their effects on various responses of interest through ordinary or generalized regression models, which can serve as concurrent validations. We will use the Index of Readiness (IR) as a case study to describe a statistical procedure to address this problem. Our solution will allow us to propose an optimal strategy of care to increase the adherence of HIV patients to treatments, as measured by a health indicator, by improving their readiness.