I used it at labcorp when I worked at my last job, it never failed. I am hoping this was just a fluke and maybe somone messed with it. I hope this second test is good, but you should be ok I will cross my fingers for ya. But let us know either way. If you testsed on the 28th and the mro has not called to tell you there was a problem by now then you are golden, by law the mro has to talk to you if there is a failure by the federal guidelines. He or she has to see if you have any med conditions that would cause the numbers to be off i.e sg, ph ect..you not going to fail for drugs thats for sure.