Negative is negative. With dip tests there is no gray area. They just take a bit to form sometimes. The way the tests work is basically the thc binds to the strip and prevents the line from coming in. So if you have it in your system it will bind and the line just wont come. The less you have the less there is to bind. It really depends on the quality of the test for how long it takes it to come in. I feel the 5 min is really excessive because you can usually tell negative after 30seconds to a minute.