The Canadian batches contain a vial of urea crystals that need to be added to the QF solution in order to get past the uric acid checks of Canadian drug testing.

There is no concrete substantiation that any of the States are testing for uric acid. All there exists is a bunch of anecdotal accounts without any legitimate documentation to substantiate the rumors. If it was actually true that uric acid is tested for, there would have to be standards established by the SAMHSA division of the United States DHHS, complete with cutoff thresholds for all certified labs to go by ( in the same manner that creatinine, specific gravity, pH, etc; are). As anyone would notice when looking up the DHHS regs on Specimen Validity Guidance, there are no standards established for uric acid. Therefore, its improper for labs to flag a urine sample for a lack of uric acid without established standards to go by. Labs certified by the DHHS have to apply the criteria for "non-human"/"substituted" samples as outlined by the SAMHSA division of the DHHS.