Open ndunnewind opened 2 years ago
Hi @ndunnewind, sorry for the very slow response - I've been away from work for much of the last couple of years.
My intention with forcing the user to specify trt_class
even to fit the single common interaction model was that this model makes some fairly strong assumptions, and requiring trt_class
makes the user explicitly specify them.
I can see that this is a bit fiddly from a user perspective, however.
Perhaps we should allow the user to specify class_interactions = "common"
without classes in the network, and give a warning like:
warn("Using a single common interaction parameter for all treatments against the reference treatment. Specify treatment classes in the network to change this. See set_*() argument `trt_class`.")
This could maybe be demoted to a note with inform()
if the user has explicitly set trt_ref
.
What do you think? Happy to review a PR (if you're still interested 2 years later!)
Hi @dmphillippo. According to Dias 2018[^1] (page 239-240), in a meta-regression model with a common interaction "there is a single interaction term b that applies to relative effects of all the treatments relative to treatment 1". However, when trying to fit such a model, multinma requires treatment classes to be specified in the network.
A solution would be to manually define the treatment classes "placebo" and "treatment".
Would you accept a PR that allows
class_interactions = "common"
without specified treatment classes in the network?nma()
would then simply assume there are two classes: one for the reference treatment, and one for all others. Maybe this should only work if the user explicitly set atrt_ref
in the network and/or with a regression formula without an interaction with the treatment (class), i.e.~ stroke
.[^1]: Dias, S., Ades, A. E., Welton, N. J., Jansen, J. P., & Sutton, A. J. (2018). Network meta-analysis for decision-making. John Wiley & Sons.