G/F just did the "control."
It stains just like mine, but it is becoming negative; slowly though.
Sorry about the pics, I was trying to be thorough and maybe educate too.

I can only conclude that mine too is negative.
I have been on a regimine of Creatine, Natural Herb Cranberry Pills with Vitamin C, Green Tea, and GNC's Liver detox with Milk Thistle, Green Tea leaf extract, Vitamin C, E, B-6, and B-12.

I don't know if this is the cause of my being negative since I was alread borderline somewhat negative according to the home drug test.
I think Not Smoking is key.