My project study the association between coinfection by hepatitis virus and survival among HIV-infected patients. Two opposite data exist: some studies show significant worse survival for patients with coinfection by hepatitis virus than those without coinfection; other studies show non-significant of survival between these two groups. I believe it happens not uncommon that inconsistent data regarding the same topic. So, I would like to have some good opinion about how to explain the different results? For instance, different population used in different study could be one factor, the number of event differ, and others?
My question is regarding general problem, not specifically pointing to some studies.