As per regulatory guidelines it is not necessary to use any test or nither test is suggested by the regulatory.
You have to find out the cmax for each period for each subject and whatever is the concentration value in the predose sample for the specified subject and specified period, check whether it is greater than 5% of cmax.
If it is so then exclude that subject from the pharmacokinetic as well as statisical analysis.
If not then include that subject with the actual concentration value for the same.
If your study passes in the boundry line then produce both the results in your repot.
Hope this will clear your doubt,