Sorry to hear about your relapse.
If it is 80 hour screen then they are testing for EtG. In that case I would try and postpone until at least 72 hours or more have passed. So much depends on when the last drink was had and how long until it was all metabolized. Alcohol may have been in your system until early the next morning. So that is when you would start the hour counting.
Also this is a tricky and fairly unreliable test as using mouthwash and other medicines that contain alcohol will result in a positive test.
I can only imagine the stress. Regardless of the test outcome keep up the good work and contnue build on that 3.5 months.