Convergence Assessment in Latent Variable Models: Application to the Longitudinal Modelling of a Marker of HIV Progression

Infection’ with Human Immunodeficiency Virus type-1 (HIV-1), the virus that leads to AIDS, is associated with a decline in CD4 cell count, a type of white blood cell involved in the immune system. In order to monitor the health status and disease progression of HIV infected patients, CD4 counts have thus been frequently used as a marker. In particular, Markov process models of the natural history of HIV play an important part in AIDS modelling (Longini et al., 1991, Freydman, 1992, Longini, Clark and Karon, 1993, Gentleman et al., 1994, Satten and Longini, 1996).