There's a good chance the nurse or phlebotomist that did the test may have done it wrong.
At least when I worked, 7 years ago, we had to make sure the blood draw was done in a pretty specific way and if it isn't done right, then it needs to be redone.
It is an important test though, so I would make sure to do it. It tests for a wide range of diseases, many quite serious, like cystic fibrosis and phenylketonuria ( the pku in the name)
Good luck hun!