Figure 2

Kaplan-Meier failure curves for time between recurrent events. The percent of at risk patients that have a recurrent event (y-axis) over time since their previous event (x-axis) is displayed. For example, all patients with a first event are at risk for a 1^st recurrence (solid black line). At 1 year after their first event, 26% of these children have had a 1^st recurrence. The time between events significantly decreased with each increasing event number (p < 0.0001; derived from a Wald test of event number (modeled as an ordinal variable) in a Prentice, Williams and Peterson gap time (PWP-GT) Cox proportional hazards model for time between events).