Kaplan-Meier method

In these analyses, the Kaplan-Meier method was used to generate age-of-onset-curves. Eigure 1 shows not only that the onset distributions were similar across countries, but also that more than 50% of the cases had their first onset before age 20. Even the proportion of individuals with a first manifestation of anxiety disorder before age 10 is remarkably high. After age 40, the risk for... 

Liver dysfunction. In a 4-year study in 1221 liver dysfunction-free (serum aspartate aminotransferase [AST] and alanine aminotransferase [ALT] <39 lU/L and no medical care for or no past history of liver disease) males aged 35-56 years, was investigated for the association of coffee consumption with the development of increased serum AST and/or ALT activities. From the analysis using the Kaplan-Meier method, the estimated incidence of serum AST and/ or ALT > 40 lU/L, > 50 lU/L, and > 60 lU/ L decreased with an increase in coffee consumption. From the Cox proportional haz-... 

If for some reason patients leave the study, renormalization is usually made by the Kaplan-Meier method (2). 

Fig. 4.9. Overall survival probabilities stratified by tumor oxygenation status, estimated by Kaplan-Meier methods for patients with advanced cancers of the uterine cervix (modified from Hockel et al. 1996b). n = number of patients...

Fig. 3.1.2. Survival data calculated by the Kaplan-Meier method for patients with hepatocellular carcinoma (HCC) treated only with (-) TACE n = 123) or patients n = 32) treated with (—) the combined treatment protocol (TACE followed by LITT). The mean survival of patients with TACE treatment was 25.0 months and significant lower than the median survival of 36.0 months in patients treated with the combined protocol...

The Nd-YAG laser fiber was introduced with a per-cutaneously positioned irrigated laser application system. Qualitative and quantitative MR parameters and clinical data were evaluated. Survival data were calculated using the Kaplan-Meier method. 

In total, 26 patients (16 males, 10 females average age 57 years range, 40-76 years) were treated. The total number of treated metastases was 69, ablated in 50 treatment sessions. The mean number of treated lesions per patient was 2.7. Survival rates were calculated using the Kaplan-Meier method. We included patients with fewer than five metastases with a maximum diameter of 5 cm. Of the patients 19.2% had recurrent metastases after surgery, 57.7%... 

Survival curves were evaluated using the Kaplan-Meier method (Kaplan and Meier 1958). The mean cumulative survival rate of patients with colorectal liver metastases was 3.8 years (95% confidence interval 3.4-4.1 years) (Fig. 25.9). The 1-year survival rate was 93%, the 2-year survival rate was 73%, the... 

These methods are essential when there is any significant degree of mortality in a bioassay. They seek to adjust for the differences in periods of risk individual animals undergo. Life table techniques can be used for those data where there are observable or palpable tumors. Specifically, one should use Kaplan-Meier product limit estimates from censored data graphically, Cox-Tarone binary regression (log-rank test), and Gehan-Breslow modification of Kruskal-Wallis tests (Thomas et al., 1977 Portier and Bailer, 1989) on censored data. 

The Kaplan-Meier estimates produce a step function for each group and are plotted over the lifetime of the animals. Planned, accidentally killed, and lost animals are censored. Moribund deaths are considered to be treatment related. A graphical representation of Kaplan-Meier estimates provide excellent interpretation of survival adjusted data except in the cases where the curves cross between two or more groups. When the curves cross and change direction, no meaningful interpretation of the data can be made by any statistical method because proportional odds characteristic is totally lost over time. This would be a rare case where treatment initially produces more tumor or death and then, due to repair or other mechanisms, becomes beneficial. 

The Kaplan-Meier estimate is a nonparametric method that requires no distributional assumptions. The only assumption required is that the observations are independent. In the case of this example, the observations are event times (or censoring times) for each individual. Observations on unique study participants can be considered independent. The confidence interval approach described here is consistent with the stated preference for estimation and description of risks associated with new treatments. A method for testing the equality of survival distributions is discussed in Chapter 11. 

Details of statistical analyses for potential toxicities that should be explicitly considered for all products and AEs of special interest Aiialyses for these events will in general be more comprehensive than for standard safety parameters. These analyses may include subject-year adjusted rates, Cox proportional hazards analysis of time to first event, and Kaplan-Meier curves. Detailed descriptions of the models would typically be provided. For example, if Cox proportional hazards analysis is specified, a detailed description of the model(s) that will be used should be provided. This would generally include study as a stratification factor, covariates, and model selection techniques. More advanced methods, such as multiple events models or competing risk analyses, should be described if used (as appropriate). It is recommended that graphical methods also be employed, for example, forest plot and risk-over-time plot (Xia et al., 2011). 

Nonparametric analysis provides powerful results since the rehahility calculation is unconstrained to fit any particular pre-defined lifetime distribution. However, this flexibility makes nonparametric results neither easy nor convenient to use for different purposes as often encountered in engineering design (e.g., optimization). In addition, some trends and patterns are more clearly identified and recognizable with parametric analysis. Several possible methods can be used to fit a parametric distribution to the nonparametric estimated rehability functions (as provided by the Kaplan-Meier estimator), such as graphical procedures or inference procedures. See Lawless (2003) for details. We choose in this paper the maximum likelihood estimation (MLE) technique, assuming that the sateUite subsystems failure data are arising from a WeibuU piobabihly distribution, as expressed in Equations 1,2. 

The assessment of patency of an implanted vascular graft or operation technique is a special modality of a clinical study. Valid comparisons on vascular access patency rates can be made only if patency is defined in a way that can be universally used by all specialties in a consistent manner [10]. Kaplan-Meier analysis is the most commonly used life table method in medical practice. It adequately copes with the issues such as patients for whom the event has not yet occurred and for those lost to follow-up. The data required by the method include the time of commencement of the treatment and the time the measured event occurred (e.g. thrombosis, infection). Patients who dropped out of treat-... 

The analysis method attributed to Kaplan and Meier (1958) enables us to analyze the time to the first reported AE while accounting for different lengths of time at risk. To illustrate this method fully, we have modified the data from the previous example slightly, as shown in Figure 8.2. We refer to this new example as study 2. 

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