As part of developing a study, I have created some study packages with different levels of covariates. One contains the full OHDSI-recommended large-scale propensity score, while others specify either no covariates, covariates only as Age + Charlson Comorbidity Index, or covariates only Age + Sex.
The attrition tables show that when the study package is run with no covariates, even when there are quite a few subjects in the cohorts, the population drops to 0 at the stage “Matched on propensity score”. Of course we are not planning on running a study without any covariates, but are curious why this might be the case (hopefully, the answer might help with fixing errors in other versions of the package). Does anyone have any ideas?