Building a Treeage Markov Model

To add the number of QALYs associated with transitioning from remission to remission, select the
“Remission” terminal node of the “Remission” subtree coming out of the Markov node. Select
Node/Values List/Markov Info, or go to the top of your screen, click on the symbol that represents Markov
information (includes an “M” with a circle around it). In the box that opens, click on the row that
corresponds to Transition Reward 2, which is the row labeled “Trans 2” that follows the row labeled “All
Sets (Unused+Active).” In the column labeled “Value” type in 0.9. To discount this value, divide by (1+r)^_
stage, so the whole expression is: 0.9/((1+r)^ stage). Push “Enter.”
To display outcome information in the tree, go to “Edit/TreePreferences/Display/Variables/Markov Info and
select “Show Definitions.”
To prepare the tree for a cost-effectiveness analysis, go to “Edit/TreePreferences/Calculation/Calculation
Method/Cost-Effectiveness, and make sure “Cost payoff” is number 1 and “Effectiveness payoff” is
number 2. If the program says “C-E calculation method is not active. Do you want to activate it now?”
click “Yes.” Click on “Numeric Formatting,” and three boxes should appear. In all three, select 2 “Decimal
places,” “Add trailing zeros,” “Use thousands separator,” and “Show numbers” exactly. In the top most
box select “Units : Currency.” In the middle box, select “Units: Custom suffix” and “Prefix/suffix: QALYs.”
In the lowest box select “Units: None.”
Save your partially completed Markov model in *.trex format (“File/
save As ...”) in a file labeled with your last name followed by the number 8, for example, Williams8.
Repeat these steps to add discounted values for cost as Transition Reward 1 and discounted values for
Quality Adjusted Life Years as Transition Reward 2 to other terminal nodes, including the nodes for
“Death,” even when those values are zero.
If you want to avoid the tedium of adding all these values, download “Lupus Markov model 1" from the
assignments section of Blackboard, which has these values already added.
Even though you are not going to use stage rewards in this exercise, the program requires that there be
stage rewards. Check the stage rewards in the tree (they are located underneath the four branches of the
Markov node) to make sure all of them have values of zero. If any do not have the value of zero, go to the
top of your screen, click on the symbol that represents Markov information (includes an “M” with a circle
around it), and put zeros in the locations for stage rewards.
Tell the program how many cycles it should run
12. Select the Markov node, go to the top of your screen, select Node/Values List/Markov Info, or click on
the symbol that represents Markov information (includes an “M” with a circle around it). A panel should
appear at the bottom of your screen with the name “Termination conditions.” In the row labeled “Term” in
the column labeled “Value” type in STAGE>1999.
Define values for the variables you have created
Select the “Lupus” node, go to the top of your screen, select Node/Define Variable, or click on the symbol
at the top (and the bottom right) of your screen that includes “V=” twice, one over the top of the other. A
panel should appear with the names of the variables you have created. Select “cHosp” and assign it the
value of 10000 in the box that pops up. Repeat the process to assign the value of 0.03 to “r.” Repeat the
process and select stage. In the box that pops up there is a section labeled “Groups:” which is
immediately below the section labeled “_stage =”. In this section, select “Keywords.” Doing this activates
a list of words in the section labeled “Element:,” which is to the right. In this section, double click “_stage.”
Check to make sure that at the top of the box you have “ stage `= stage.”
Your tree should look like the following tree:
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