Time-to-Event Analysis for Onset of Neurological Symptoms and for Survival Duration.1–3

Testing Terms: In Kaplan-Meier analysis the Log-Rank test places more weight on later event times; the Wilcoxon test places more weight on early event times and is the optimum rank test if the error distribution is logistic. Prob > ChiSq lists the probability of obtaining, by chance alone, a Chi-square value greater than the one computed if the time-to-event functions are the same for all groups. In Cox proportional hazards analysis the Effect Likelihood Test is the likelihood-ratio Chi-square test on the null hypothesis that the parameter estimate for the Treatment covariate is zero (no effect of treatment). Testing term descriptions are taken from the JMP 10.0.0 Help file. A neurological score of two in both hind limbs is taken to be the definitive onset of neurological symptoms. Animals that did not reach a neurological severity score of 2 prior to termination of the experiment at 180 days of age were right-censored in the onset analysis. Animals that did not die by 180 days of age were right-censored in the survival analysis.Time-to-Event Analysis for Onset of Neurological Symptoms and for Survival Duration.1–3