I am calculating area under the curve (AUC) values for the individual independent variables of a conditional logistic regression model. I am using Stata's rocreg command.

Half of the ten variables show AUC values below 0.5, specifically values as 0.32, 0.38 and 0.45.

Do AUC values below 0.5 indicate data error? If not, can the values simply ble inverted (so that I present AUC of 0.32 rather as 0.68), or must they be reported as they are?

The study is a matched case control study with 12 cases and two matched controls for each case.

Thank you in advance.