Moving to state after fixed number of cycles


 I am building a state transition Markov model for anti-depression drug. 

The patients enter the model 100% in "depressed" state from where they can move to "remission" or "die", or they can stay in "depressed" state.

When patients are in "remission" they can stay there, and experience a relapse back to depression or die. And there is one more state in the model -  "recovery" to where patients can get if they stay in "remission" for 4 consecutive cycles. I understand this memory is introduced using a tunnel function, but fail to figure out how exactly this is programmed. 

Thank you!



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  • Official comment


    The Recovery State in your model just needs to be set as a tunnel state, where you set the maximum number of tunnels you want to count. In your case, that sounds like 4.

    The turn on the tunnel state:

    1. Select the Remmision State node.
    2. Open the Markov View and then you should see the Tunnel Max at the bottom of the list.
    3. Set the Tunnel Max to 4.

    This now makes available the keyword _tunnel which you can reference in the model. For example:

    if(_tunnel < 4; 1; 0)

    This expression is TRUE when you have been in Remission for less than 4 cycles. So you can use this (or similar expression) to direct the cohort to the appropriate state.

    You can also find more about Tunnels in the Help. Just search for Tunnels and look at the appropriate section. Feel free to email support AT if you need further assistance.

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