I am looking at a blood biomarker (continuous)'s ability to predict gestational diabetes (binary outcome). I have 208 women without the outcome (controls), and 56 women with the outcome (cases). I wish to know what is my power for detecting a meaningful difference of an Odds Ratio of 1.5. Importantly, the blood biomarker is protective of the outcome, i.e. women with the outcome have lower levels of the biomarker.

According to the STATA help manual for powerlog, it says that "p2 = estimated probability of a 1 at the mean + 1 sd of the predictor", does this assume that there is a positive association between the predictor or outcome? I am wondering whether I should calculate p2 as the mean minus 1sd of the predictor in my case?

I also am not sure how/where to factor in the OR 1.5 I am trying to detect..

Lastly, how can I input the sizes of my control and cases group, e.g. can I type:

powerlog, p1(x) p2(y) n1(56) n2(208)?
or powerlog, p1(x) p2(y) n1(208) n2(56)?

I am using STATA version 16. The powerlog command is externally installed.

Thank you so much for everyone/anyone's help!