![Flow diagrams depicting the Markov Model of Disease Progression. Go to Text Description [D] for details.](dcappfig1.gif)
The model is used to follow the disease progression of all members of a cohort simultaneously on five different disease paths. For the simulation, transitions between states take place at discrete time intervals 1 year apart. Thus, at the end of each 1 year period, portions of the cohort can move from one disease state to another or stay in the same disease state. The simulation program determines what proportion of the cohort will move from one state to another based on the transition probability. In several cases, an individual can experience a complication event that the patient either dies of or survives during the period.
The Markov model keeps track of the number of patients who are in each state in each period. It also keeps track of the cumulative incidence of patients who have undergone complication events such as lower extremity amputation (LEA), angina, cardiac arrest (c) or myocardial infarction (MI), and stroke. In the diagrams, complication events are represented by diamonds; states are numbered and represented by ovals.