Generalized Patient Flow Model

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We start with a normal population of people who are not afflicted, of which a fraction develop a disease over time. These new cases arising per year are referred to as the true incidence rate. These new cases flow into a stock of undiagnosed patients, some of whom die undiagnosed and some are seen by clinicians, diagnosed and placed on treatment. This flow from undiagnosed to diagnosed is referred to as the diagnosed incidence and the rate of flow is the diagnosis rate. Some diseases with the rapid onset of unpleasant symptoms are diagnosed and treated quickly, whereas chronic diseases with insidious onset, like dementia, diabetes and hypertension can take years to diagnose. On being diagnosed and treated, patients flow into the stock of currently treated patients. From here they can die treated or discontinue, then later re-initiate treatment.



Fig. 1 - Incidence [Source]

Adding Diagnosed

Fig. 2 - Incidence and Diagnosis [Source]

Adding Treated

Fig. 3 - Incidence, Diagnosis and Treatment [Source]

Virtual Experiments

Fig. 4 - Simulation Run Results [Source]


  • Mark Paich, Corey Peck and Jason Valant (2011) Pharmaceutical market dynamics and strategic planning: a system dynamics perspective System Dynamics Review 27(1)47-63
  • Paich M, Peck C and Valant J Pharmaceutical Product Strategy Using Dynamic Modeling for Effective Brand Planning Informa Health Care New York 2008 Book
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