If an individual has been validly baptized, then that person is a Christian.
If an individual is able to confess the Faith, as stated in the Creed First Ecumenical Council of Constantinople-Nicea, then that individual is a professing Christian.
If that individual endeavors to live his life in accordance with the Gospel (to whatever the degree the individual does so is irrelevant), then that individual is a practicing Christian.
Please note that whether the person is in communion with the Bishop of Rome was not listed as one of the criteria.