Tracker in Markov cohort

Hi all! I would like the event probabilities and costs to vary based on the time a medical device has been in use, with the usage time reset when the device is replaced. The tracker was tested in the model, whereas this cannot function normally in the Markov cohort and Tornado diagram (the value always used the initial value of the tracker). How do I make the Markov cohort and Tornado diagram function normally?

Example 1:

{T} DeviceA = DeviceA+1

Probability of Failure: DeviceFailure[DeviceA]

Example 2:

{T} InFail_DeviceA = InFail_DeviceA+1

{T} AgeInFail_DeviceA = if (InFail_DeviceA=1;Age;AgeInFail_DeviceA)

if (AgeInFail1_DeviceA>2;cDeviceA;0)

Thanks for helping!



  • Official comment

    If you use trackers, then you must run Microsimulation for all analyses, including...

    • Base case - Microsimulation
    • Tornado - check box to run Microsimulation
    • PSA - run both Sampling and Trials (PSA and Microsimulation)

    So you can still run Tornado analysis. Just check the box to run Microsimulation for each model calculation within the context of the Tornado diagram.



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  • Hi Andrew,

    Thanks for answering!

    I tried the Microsimulation, but the new problem is:

    • Why is this kind of formula in the probability different in microsimulation outputs?

              Formula: if(_stage=0;pExp1;pExp2)
              Both the pExp1 and pExp2 are constant.

    For example: in stage 0, the probability is 0.001 in Microsimulation 1, but it is 0.004 in Microsimulation 2.

    • Can trackers work in the Trans Cost below when using Microsimulation?

              Tracker in forward nodes: if(_stage=0;pExp1;pExp2)
                Node1: InFail=InFail+1
                Node2: if(InFail=1;Age;AgeInFail)
              Trans Cost: if (AgeInFail>5;cDevicce+cSurgery;cSurgery)

    Thank you for your assistance.

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  • I cannot examine the calculations above without the model. I think it's best to make your request in a support ticket rather than a forum. That way you can send the model and point to what you think is not working correctly. You can email the question and model to

    You can use trackers anywhere in the model including Trans Cost.


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