PubMed · 14593470
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
U Marcus, W Kiehl, O Hamouda. 2003. [Current developments in syphilis. Prevention].. https://doi.org/10.1007/s00105-003-0606-2
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The generalized additive, model (GAM) is a powerful and widely used tool that allows researchers to fit, non-parametrically, the effect of continuous predictors on a transformation of the mean response variable. Such a transformation is given by a so-called link function, and in GAMs this link function is assumed to be known. Nevertheless, if an incorrect choice is made for the link, the resulting GAM is misspecified and the results obtained may be misleading. In this paper, we propose a modified version of the local scoring algorithm that allows for the non-parametric estimation of the link function, by using local linear kernel smoothers. To better understand the effect that each covariate produces on the outcome, results are expressed in terms of the non-parametric odds ratio (OR) curves. Bootstrap techniques were used to correct the bias in the OR estimation and to construct point-wise confidence intervals. A simulation study was carried out to assess the behaviour of the resulting estimates. The proposed methodology was illustrated using data from the AIDS Register of Galicia (NW Spain), with a view to assessing the effect of the CD4 lymphocyte count on the probability of being AIDS-diagnosed via Tuberculosis (TB). This application shows how the link's flexibility makes it possible to obtain OR curve estimates that are less sensitive to the presence of outliers and unusual values that are often present in the extremes of the covariate distributions.
In many settings, one would expect that the hazard for a terminal event would change with the occurrence of an intermediate event. For example, in an AIDS clinical trial, it is of interest to assess whether there is a difference between treatments in the hazards for death prior to drop in Karnofsky performance score and in the hazards subsequent to the drop in Karnofsky score. Tests for the effect of treatment on these hazard functions, separately or jointly, are useful in conjunction with tests of overall survival. We consider four Cox regression models for the hazard function, constructed by allowing for various combinations of time-dependent stratification and time-dependent covariates, both of which are based on the occurrence of the intermediate event. Assuming a Markov transition model from the intermediate to the terminal event, partial likelihoods can be used for inference, enabling the use of standard statistical software for computation. We develop analytic approximations for the power of the derived score tests for treatment differences in the hazard functions and evaluate them through simulations. We apply our results to AIDS Clinical Trials Group (ACTG) protocol 021.
In 2001, CDC, the National Institutes of Health, and the Infectious Diseases Society of America convened a working group to develop guidelines for therapy of human immunodeficiency virus (HIV)-associated opportunistic infections to serve as a companion to the Guidelines for Prevention of Opportunistic Infections Among HIV-Infected Persons. In recognition of unique considerations related to HIV infection among infants, children, and adolescents, a separate pediatric working group was established. Because HIV-infected women coinfected with opportunistic pathogens might be more likely to transmit these infections to their infants than women without HIV infection, guidelines for treating opportunistic pathogens among children should consider treatment of congenitally acquired infections among both HIV-exposed but uninfected children and those with HIV infection. In addition, the natural history of opportunistic infections among HIV-infected children might differ from that among adults. Compared with opportunistic infections among HIV-infected adults, which are often caused by reactivation of pathogens acquired before HIV infection when host immunity was intact, opportunistic infections among children often reflect primary acquisition of the pathogen and, among children with perinatal HIV infection, infection acquired after HIV infection has been established and begun to compromise an already immature immune system. Laboratory diagnosis of opportunistic infections can be more difficult with children. Finally, treatment recommendations should consider differences between adults and children in terms of drug pharmacokinetics, dosing, formulations, administration, and toxicities. This report focuses on treatment of opportunistic infections that are common in HIV-exposed and infected infants, children, and adolescents in the United States.