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Recursos bibliográficos en papel y digitales -
- libros, artículos de revistas,
ponencias de eventos, etc. -
» Resultado: 4 registros
| Registro 1 de 4 | |
| Autor: | Zheng, Yingye - Heagerty, Patrick, J. |
| Título: | Prospective accuracy for longitudinal markers |
| Fuente: | Biometrics. v.63, n.2. International Biometric Society |
| Páginas: | pp. 332-341 |
| Año: | jun. 2007 |
| Resumen: | In this article we focus on appropriate statistical methods for characterizing the prognostic value of a longitudinal clinical marker. Frequently it is possible to obtain repeated measurements. If the measurement has the ability to signify a pending change in the clinical status of a patient then the marker has the potential to guide key medical decisions. Heagerty, Lumley, and Pepe (2000, Biometrics 56, 337-344) proposed characterizing the diagnostic accuracy of a marker measured at baseline by calculating receiver operating characteristic curves for cumulative disease or death incidence by time t. They considered disease status as a function of time, D(t) = 1(T = t), for a clinical event time T. In this article we aim to address the question of how well Y(s), a diagnostic marker measured at time s(s = 0, after the baseline time) can discriminate between people who become diseased and those who do not in a subsequent time interval [s, t]. We assume the disease status is derived from an observed event time T and thus interest is in individuals who transition from disease free to diseased. We seek methods that also allow the inclusion of prognostic covariates that permit patient-specific decision guidelines when forecasting a future change in health status. Our proposal is to use flexible semiparametric models to characterize the bivariate distribution of the event time and marker values at an arbitrary time s. We illustrate the new methods by analyzing a well-known data set from HIV research, the Multicenter AIDS Cohort Study data. |
| Solicitar por: | HEMEROTECA B + datos de Fuente |
| Registro 2 de 4 | |
| Autor: | Zheng, Yingye - Cai, Tianxi - Feng, Ziding - |
| Título: | Application of the time-dependent ROC curves for prognostic accuracy with multiple biomarkers |
| Fuente: | Biometrics. v.62, n.1. International Biometric Society |
| Páginas: | pp. 279-287 |
| Año: | mar. 2006 |
| Resumen: | The rapid advancement in molecule technology has led to the discovery of many markers that have potential applications in disease diagnosis and prognosis. In a prospective cohort study, information on a panel of biomarkers as well as the disease status for a patient are routinely collected over time. Such information is useful to predict patients’ prognosis and select patients for targeted therapy. In this article, we develop procedures for constructing a composite test with optimal discrimination power when there are multiple markers available to assist in prediction and characterize the accuracy of the resulting test by extending the time-dependent receiver operating characteristic (ROC) curve methodology (b11Heagerty, Lumley, and Pepe, 2000, Biometrics56, 337-344). We employ a modified logistic regression model to derive optimal linear composite scores such that their corresponding ROC curves are maximized at every false positive rate. We provide theoretical justification for using such a model for prognostic accuracy. The proposed method allows for time-varying marker effects and accommodates censored failure time outcome. When the effects of markers are approximately constant over time, we propose a more efficient estimating procedure under such models. We conduct numerical studies to evaluate the performance of the proposed procedures. Our results indicate the proposed methods are both flexible and efficient. We contrast these methods with an application concerning the prognostic accuracies of expression levels of six genes. |
| Solicitar por: | HEMEROTECA B + datos de Fuente |
| Registro 3 de 4 | |
| Autor: | Heagerty, Patrick J. - Zheng, Yingye - |
| Título: | Survival model predictive accuracy and ROC curves |
| Fuente: | Biometrics. v.61, n.1. International Biometric Society |
| Páginas: | pp. 92-105 |
| Año: | mar. 2005 |
| Resumen: | The predictive accuracy of a survival model can be summarized using extensions of the proportion of variation explained by the model, or R 2, commonly used for continuous response models, or using extensions of sensitivity and specificity, which are commonly used for binary response models. In this article we propose new time-dependent accuracy summaries based on time-specific versions of sensitivity and specificity calculated over risk sets. We connect the accuracy summaries to a previously proposed global concordance measure, which is a variant of Kendall’s tau. In addition, we show how standard Cox regression output can be used to obtain estimates of time-dependent sensitivity and specificity, and time-dependent receiver operating characteristic (ROC) curves. Semiparametric estimation methods appropriate for both proportional and nonproportional hazards data are introduced, evaluated in simulations, and illustrated using two familiar survival data sets. |
| Solicitar por: | HEMEROTECA B + datos de Fuente |
| Registro 4 de 4 | |
| Autor: | Zheng, Yingye - Barlow, William E. - Cutter, Gary |
| Título: | Assessing accuracy of mammography in the presence of verification bias and intrareader correlation |
| Fuente: | Biometrics. v.61, n.1. International Biometric Society |
| Páginas: | pp. 259-268 |
| Año: | mar. 2005 |
| Resumen: | The performance of a medical diagnostic test is often evaluated by comparing the outcome of the test to the patient’s true disease state. Receiver operating characteristic analysis may then be used to summarize test accuracy. However, such analysis may encounter several complications in actual practice. One complication is verification bias, i.e., gold standard assessment of disease status may only be partially available and the probability of ascertainment of disease may depend on both the test result and characteristics of the subject. A second issue is that tests interpreted by the same rater may not be independent. Using estimating equations, we generalize previous methods that address these problems. We contrast the performance of alternative estimators of accuracy using robust sandwich variance estimators to permit valid asymptotic inference. We suggest that in the context of an observational cohort study where rich covariate information is available, a weighted estimating equations approach may be preferable for its robustness against model misspecification. We apply the methodology to mammography as performed by community radiologists. |
| Solicitar por: | HEMEROTECA B + datos de Fuente |
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