# Fixed interval cost calculations

How do I calculate the cost of the treatment which is conducted at fixed intervals (e.g. once every three weeks) in a weekly cycle model?

• Hi Tatsunori,

I think a good idea could be to create a table with the treatment cost per stage (or cycle) eg. in the first line of the table \$0, first cycle  \$100, second cycle \$0, third cycle \$0, fourth cycle \$100 and so on.

Then on the incremental cost of the Markov info you can reference the table instead of using a value or a formula eg.: tablename[_stage], (don't forget to use the [_stage] command!!), and the software will use the cost of each cycle specified in the table.

Hope this helps!,

Ruben

• Hi,

Another way is to use the modulo command. e.g.

If(modulo(_stage;3)=0;Costvariable;0)

This will count the cost every 3 weeks and is less work. Note that the '3' in the formula can be replaced with a variable if you want that to change over time.

• I also use the modulo() function. Another example would be costs for an annual screening process where the cohort (or the individual in a microsimulation) is assigned a cost for a screening test every 12 months:

if(modulo(_stage;12/CycleLength) = 0;DR*cAnnualScreening;0)

where 'CycleLength' is the cycle length in months and 'DR' is the discount function (if global discounting is not used)

• I like the Modulo approach suggested by Harpreet Singh and David Naimark.

This provides more flexibility by allowing you to run sensitivity analysis on the cost parameter (e.g., cAnnualScreening).