Housing.

As biomarkers transformable by specific drug agents increasingly become available, so their usefulness also increases for monitoring compliance in clinical and prevention trials, and for subsequent monitoring in the general population if a treatment is found successful. Marker levels measured over the course of a treatment yield a longitudinal trajectory that is typically non-linear, with varying velocities during the phase-in and steady-state periods of treatment, followed by decays back to normal in the presence of non-compliance. There is often considerable between-individual variability both in the mean parameters of the trajectory and the variability over time. An example is the biomarker mean corpuscular volume (MCV), which increases by 20 per cent from the drug zidovudine (AZT), and has been used to monitor compliance to AZT. Using MCV data from a previous AIDS clinical trial as an example, we describe a non-linear hierarchical growth model suitable for biomarkers that exhibit sigmoidal and/or asymptotic growth behaviour and show how such models can be supplemented with a change-point to identify potential times of non-compliance. We perform a fully Bayesian analysis to obtain a variety of posterior summaries for the behaviour of the longitudinal trajectory and the times of non-compliance, and describe how to obtain predictions of non-compliance for new individuals.

Acquired Immunodeficiency Syndrome↗

PubMed2002

Estimation of risk of cancers before occurrence of acquired immunodeficiency syndrome in persons infected with human immunodeficiency virus.

There is methodological debate as to whether cohorts defined by acquired immunodeficiency syndrome (AIDS) diagnosis can be used to estimate risks of cancer in persons with human immunodeficiency virus (HIV) before AIDS. The authors compared risks of non-AIDS-defining cancers before AIDS in persons with HIV using a cohort based on AIDS diagnosis and a second cohort based on HIV diagnosis. National population-based registries of AIDS and HIV diagnoses to August 1999 were matched separately with the National Cancer Registry in Australia. Four analyses were performed. In analysis 1, follow-up was from 5 years before AIDS registration in 8,118 persons with AIDS. Analysis 2 was similar but adjusted expected numbers of cancers for decreased survival. Analysis 3 was based on 7,061 persons registered with HIV, with follow-up from the reported date of diagnosis. Analysis 4 was based on 2,112 AIDS cases previously reported with HIV, with follow-up from 5 years before AIDS diagnosis. In all analyses, follow-up ended at cancer diagnosis, death, 6 months before AIDS, or the end of available cancer data, whichever occurred first. For 10 types of cancer there were at least three cases in any one of the analyses. For these cancers there was no systematic pattern such that one analysis produced consistently higher or lower estimates than the others. These analyses suggest that cancer risk in persons with HIV before AIDS diagnosis may be estimated reliably based on cancer experience 5 years before AIDS.

Acquired Immunodeficiency Syndrome↗