Screening model - entering a cohort within an age range and setting proportions for screening
I am working on a screening model with two arms: 1) screening arm where all patients are offered a blood test and 2) non-screening arm where patients non-systematically get offered a blood test (currently about 60% of people get offered this test). It's currently a decision node with 2 Markov nodes.
I had two questions I hoped I could get help with. I've attached an image of the first part of my model.
1. Is it possible for a cohort of men to enter within a range of age groups. I want men with 5-year age groups (e.g. 49-44, 45-50). I'm currently using the CurrentAge = StartAge+_stage approach so all men enter at the same age.
2. What would be the best approach to enable modelling of different proportions of the population being screened in each arm? I thought I would add an additional branch to the right of the 'Cancer free' state, with 'Screening' and 'No screening' and put the probabilities there? The transition probabilities for a diagnosis of cancer used in the screening arm are taken from an RCT where there was 90% uptake of screening. So I'm not sure if it's correct to change the screening proportions this way.
Many thanks for your time.