An Analysis of Pediatric AIDS CD4 Counts Using Flexible Random Curves
Mingao Shi, Robert E. Weiss, Jeremy M. G. Taylor · 2011
In this paper we analyze CD4 counts from infants born to HIV infected mothers. A random effects model with linear or low order polynomials in time is unsatisfactory for this longitudinal data. We develop an alternative approach based on a flexible family of models for which both the fixed and random effects as linear combinations of B-splines. The fixed and random parts are smooth functions of time and the covariance structure is parsimonious. The procedure allows estimates of each individual's smooth trajectory over time to be exhibited. Model selection, estimation and computation are discussed. Centile curves are presented that take into account the longitudinal nature of the data. We emphasize a graphical approach to the presentation of results. KEYWORDS: B-spline, Centile Curves, Empirical Bayes, Graphics, Random Effects, Residuals. 1 Introduction. We analyze data consisting of serial CD4 counts of children born to HIV infected mothers in Los Angeles. This data set is highly unb...