I am conducting a systematic review on mostly cohort studies. One part of my quality assessment is of course; if the observational study adjusted for confounding factors. I find alot of studies finding a insignificant result in univariate analysis and only a few who continue to report the multivariate analysis after such insignificant univariate analysis (which i think is logical). But;

I am doubting how to judge the adjustment for confounding of insignificant univariate studies. There is no adjustment for confounding but it seems unfair to judge these studies of lower quality.

I hope my question is clear and people can share experience.