“When a child has a biopsy what age is it that the doctor cannot tell the parent the test results?”
That will depend in large part on in what state you live, and to some extent on what sort of biopsy it is. If it can arguably be said to be related to pregnancy, the age may be lower than otherwise provided for by state law. If the child’s parents are divorced, then it will also depend on whether the parent in question is the custodial or non-custodial parent.
Generally speaking, the youngest that would be would be 16, although it may be 18.