Figure 1.

Schematic depiction of doubly truncated neurodegenerative disease data: Here L, T, and R denote the time from disease symptom onset to study entry, death, and the end of study, respectively. The solid circle (left) consists of all subjects who entered the study and are therefore not left truncated. The light grey region of the solid circle is right truncated, and consists of all subjects who entered but lived past the end of the study, i.e. {L ≤ T} ∩ {T > R}. The dotted circle (right) consists of all subjects who had an autopsy performed by the end of the study and are therefore not right truncated. The light grey region of the dotted circle is left truncated, and consists of all subjects who never entered the study but died before the end of study date, i.e. {T < L} ∩ {T ≤ R}. The observed sample is represented by the intersection of the two circles (dark grey region), and consists of all subjects who entered the study and had an autopsy performed {L ≤ T ≤ R}.