Testing, MRO's don't review negative results period. It's a waste of time and money.

Slantedeyes, that is unusual for you not to here back after taking it on Monday and it being Friday but not unheard of. Maybe they was a back up at the lab or in the shipping or whatever. If nothing on Monday maybe check with the HR department and make sure it is good on their end or they can check to make sure the lab didn't screw up and hasn't sent in the results. It's probably not the MRO's fault especially if it is negative and it's probably out of the hands of the collection site.