Semiparametric models for longitudinal data with application to CD4 cell numbers in HIV seroconverters. NLM AIDSLINE Important note: Information in this article was accurate in 1995. The state of the art may have changed since the publication date.

Click here to return to AIDSLINE main menu
DonateNow
Print this Article


Semiparametric models for longitudinal data with application to CD4 cell numbers in HIV seroconverters.

Biometrics. 1994 Sep;50(3):689-99. Unique Identifier : AIDSLINE MED/95072226
Zeger SL; Diggle PJ; Department of Biostatistics, Johns Hopkins University, Baltimore,; Maryland 21205-2179.

Abstract: The paper describes a semiparametric model for longitudinal data which is illustrated by its application to data on the time evolution of CD4 cell numbers in HIV seroconverters. The essential ingredients of the model are a parametric linear model for covariate adjustment, a nonparametric estimation of a smooth time trend, serial correlation between measurements on an individual subject, and random measurement error. A back-fitting algorithm is used in conjunction with a cross-validation prescription to fit the model. A notable feature in the application is that the onset of HIV infection is associated with a sudden drop in CD4 cells followed by a longer-term slower decay. The model is also used to estimate an individual's curve by combining his data with the population curve. Shrinkage toward the population mean trajectory is controlled in a natural way by the estimated covariance structure of the data.
Keywords: Acquired Immunodeficiency Syndrome/*IMMUNOLOGY Algorithms Analysis of Variance Biological Markers Biometry Cohort Studies *CD4 Lymphocyte Count Human HIV Infections/*IMMUNOLOGY HIV Seropositivity/*IMMUNOLOGY *Longitudinal Studies Multicenter Studies Random Allocation Support, U.S. Gov't, P.H.S. Time Factors JOURNAL ARTICLEKWDacquiredimmunodeficiencysyndrome/KWDimmunologyalgorithmsanalysisofvariancebiologicalmarkersbiometrycohortstudiesKWDcd4lymphocytecounthumanhivinfections/KWDimmunologyhivseropositivity/KWDimmunologyKWDlongitudinalstudiesmulticenterstudiesrandomallocationsupport,uKWDsKWDgov't,pKWDhKWDsKWDtimefactorsjournalarticle
950330
M9530794

Copyright © 1995 - National Library of Medicine. Reproduced under license with the National Library of Medicine, Bethesda, MD.

AEGiS is a 501(c)3, not-for-profit, tax-exempt, educational corporation. AEGiS is made possible through unrestricted funding from Boehringer Ingelheim, Bridgestone/Firestone Charitable Trust, Bristol-Myers Squibb Company, Elton John AIDS Foundation, Gill Foundation, the National Library of Medicine, Quest Diagnostics, Roche and Trimeris, and donations from users like you. Always watch for outdated information. This article first appeared in 1995. This material is designed to support, not replace, the relationship that exists between you and your doctor.

AEGiS presents published material, reprinted with permission and neither endorses nor opposes any material. All information contained on this website, including information relating to health conditions, products, and treatments, is for informational purposes only. It is often presented in summary or aggregate form. It is not meant to be a substitute for the advice provided by your own physician or other medical professionals. Always discuss treatment options with a doctor who specializes in treating HIV.

Copyright ©1980, 1995. AEGiS. All materials appearing on AEGiS are protected by copyright as a collective work or compilation under U.S. copyright and other laws and are the property of AEGiS, or the party credited as the provider of the content. .