Calculating Stage Duration Statistics in Multistage Diseases
Figure 1
A simple illustration of the counting method.
We use the method to approximate the probability distribution of stage 1 duration of a multistage disease. The top panel shows 12 patients' visits. The horizontal axis is the time elapsed from stage 1 onset, and the numbers on top of vertical arrows indicate the stage assessment for each patient. The time-axis is split into 4 unequal intervals, , with
patient visits in each. The corresponding average visit times,
, and the numbers of transiting patients,
, are calculated. In the bottom panel, the approximation
is plotted, where
.