Fetal Fibronectin Test

Jenna
Any of you momma's have the FFN test before you had your little ones?
And if so, what was the accuracy in it?
I had one 2 nights ago and it came back negative, which should mean that I won't have my twins at any time within the next two weeks but I'm questioning how accurate it really is and was just wanting to hear from some people that have had it.